diff --git a/.gitignore b/.gitignore
index 2f7896d..96ef862 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 target/
+.idea/
diff --git a/src/problem.rs b/src/fetcher.rs
similarity index 100%
rename from src/problem.rs
rename to src/fetcher.rs
diff --git a/src/lib.rs b/src/lib.rs
index 815c1ce..55b0298 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,240 +1,5 @@
 #[macro_use]
 pub mod util;
 
-mod n0006_zigzag_conversion;
-mod n0238_product_of_array_except_self;
-mod n0115_distinct_subsequences;
-mod n0099_recover_binary_search_tree;
-mod n0310_minimum_height_trees;
-mod n0128_longest_consecutive_sequence;
-mod n0274_h_index;
-mod n0241_different_ways_to_add_parentheses;
-mod n0024_swap_nodes_in_pairs;
-mod n0110_balanced_binary_tree;
-mod n0093_restore_ip_addresses;
-mod n0076_minimum_window_substring;
-mod n0124_binary_tree_maximum_path_sum;
-mod n0122_best_time_to_buy_and_sell_stock_ii;
-mod n0169_majority_element;
-mod n0162_find_peak_element;
-mod n0095_unique_binary_search_trees_ii;
-mod n0155_min_stack;
-mod n0040_combination_sum_ii;
-mod n0217_contains_duplicate;
-mod n0055_jump_game;
-mod n0106_construct_binary_tree_from_inorder_and_postorder_traversal;
-mod n0145_binary_tree_postorder_traversal;
-mod n0079_word_search;
-mod n0969_pancake_sorting;
-mod n0042_trapping_rain_water;
-mod n0108_convert_sorted_array_to_binary_search_tree;
-mod n0083_remove_duplicates_from_sorted_list;
-mod n0130_surrounded_regions;
-mod n0226_invert_binary_tree;
-mod n0027_remove_element;
-mod n0188_best_time_to_buy_and_sell_stock_iv;
-mod n0204_count_primes;
-mod n0268_missing_number;
-mod n0214_shortest_palindrome;
-mod n0231_power_of_two;
-mod n0202_happy_number;
-mod n0075_sort_colors;
-mod n0066_plus_one;
-mod n0028_implement_strstr;
-mod n0290_word_pattern;
-mod n0048_rotate_image;
-mod n0089_gray_code;
-mod n0147_insertion_sort_list;
-mod n0084_largest_rectangle_in_histogram;
-mod n0011_container_with_most_water;
-mod n0009_palindrome_number;
-mod n0058_length_of_last_word;
-mod n0080_remove_duplicates_from_sorted_array_ii;
-mod n0030_substring_with_concatenation_of_all_words;
-mod n0060_permutation_sequence;
-mod n0071_simplify_path;
-mod n0038_count_and_say;
-mod n0144_binary_tree_preorder_traversal;
-mod n0279_perfect_squares;
-mod n0304_range_sum_query_2d_immutable;
-mod n0292_nim_game;
-mod n0264_ugly_number_ii;
-mod n0132_palindrome_partitioning_ii;
-mod n0019_remove_nth_node_from_end_of_list;
-mod n0136_single_number;
-mod n0018_4sum;
-mod n0220_contains_duplicate_iii;
-mod n0299_bulls_and_cows;
-mod n0232_implement_queue_using_stacks;
-mod n0100_same_tree;
-mod n0171_excel_sheet_column_number;
-mod n0087_scramble_string;
-mod n0704_binary_search;
-mod n0219_contains_duplicate_ii;
-mod n0086_partition_list;
-mod n0082_remove_duplicates_from_sorted_list_ii;
-mod n0228_summary_ranges;
-mod n0020_valid_parentheses;
-mod n0017_letter_combinations_of_a_phone_number;
-mod n0312_burst_balloons;
-mod n0306_additive_number;
-mod n0283_move_zeroes;
-mod n1018_binary_prefix_divisible_by_5;
-mod n0201_bitwise_and_of_numbers_range;
-mod n0109_convert_sorted_list_to_binary_search_tree;
-mod n0101_symmetric_tree;
-mod n0098_validate_binary_search_tree;
-mod n0035_search_insert_position;
-mod n0050_powx_n;
-mod n0198_house_robber;
-mod n0004_median_of_two_sorted_arrays;
-mod n0221_maximal_square;
-mod n0047_permutations_ii;
-mod n0172_factorial_trailing_zeroes;
-mod n0054_spiral_matrix;
-mod n0053_maximum_subarray;
-mod n1046_last_stone_weight;
-mod n0146_lru_cache;
-mod n0126_word_ladder_ii;
-mod n0242_valid_anagram;
-mod n0112_path_sum;
-mod n0023_merge_k_sorted_lists;
-mod n0230_kth_smallest_element_in_a_bst;
-mod n0104_maximum_depth_of_binary_tree;
-mod n0258_add_digits;
-mod n0187_repeated_dna_sequences;
-mod n0025_reverse_nodes_in_k_group;
-mod n0039_combination_sum;
-mod n0107_binary_tree_level_order_traversal_ii;
-mod n0091_decode_ways;
-mod n0056_merge_intervals;
-mod n0065_valid_number;
-mod n0016_3sum_closest;
-mod n0096_unique_binary_search_trees;
-mod n0072_edit_distance;
-mod n0044_wildcard_matching;
-mod n0239_sliding_window_maximum;
-mod n0174_dungeon_game;
-mod n0073_set_matrix_zeroes;
-mod n0078_subsets;
-mod n0037_sudoku_solver;
-mod n0033_search_in_rotated_sorted_array;
-mod n0002_add_two_numbers;
-mod n0313_super_ugly_number;
-mod n0068_text_justification;
-mod n0064_minimum_path_sum;
-mod n0218_the_skyline_problem;
-mod n0125_valid_palindrome;
-mod n0210_course_schedule_ii;
-mod n0143_reorder_list;
-mod n0164_maximum_gap;
-mod n0097_interleaving_string;
-mod n0105_construct_binary_tree_from_preorder_and_inorder_traversal;
-mod n0167_two_sum_ii_input_array_is_sorted;
-mod n0034_find_first_and_last_position_of_element_in_sorted_array;
-mod n0094_binary_tree_inorder_traversal;
-mod n0052_n_queens_ii;
-mod n0121_best_time_to_buy_and_sell_stock;
-mod n0273_integer_to_english_words;
-mod n0225_implement_stack_using_queues;
-mod n0046_permutations;
-mod n0085_maximal_rectangle;
-mod n0135_candy;
-mod n0113_path_sum_ii;
-mod n0029_divide_two_integers;
-mod n0260_single_number_iii;
-mod n0140_word_break_ii;
-mod n0149_max_points_on_a_line;
-mod n0213_house_robber_ii;
-mod n0222_count_complete_tree_nodes;
-mod n0134_gas_station;
-mod n0057_insert_interval;
-mod n0173_binary_search_tree_iterator;
-mod n0077_combinations;
-mod n0005_longest_palindromic_substring;
-mod n0041_first_missing_positive;
-mod n0026_remove_duplicates_from_sorted_array;
-mod n0166_fraction_to_recurring_decimal;
-mod n0119_pascals_triangle_ii;
-mod n0012_integer_to_roman;
-mod n0223_rectangle_area;
-mod n0229_majority_element_ii;
-mod n0061_rotate_list;
-mod n0123_best_time_to_buy_and_sell_stock_iii;
-mod n0301_remove_invalid_parentheses;
-mod n0067_add_binary;
-mod n0049_group_anagrams;
-mod n0189_rotate_array;
-mod n0001_two_sum;
-mod n0275_h_index_ii;
-mod n0103_binary_tree_zigzag_level_order_traversal;
-mod n0137_single_number_ii;
-mod n0208_implement_trie_prefix_tree;
-mod n0300_longest_increasing_subsequence;
-mod n0118_pascals_triangle;
-mod n0010_regular_expression_matching;
-mod n0013_roman_to_integer;
-mod n0209_minimum_size_subarray_sum;
-mod n0227_basic_calculator_ii;
-mod n0022_generate_parentheses;
-mod n0008_string_to_integer_atoi;
-mod n0152_maximum_product_subarray;
-mod n0014_longest_common_prefix;
-mod n0070_climbing_stairs;
-mod n0233_number_of_digit_one;
-mod n0154_find_minimum_in_rotated_sorted_array_ii;
-mod n0127_word_ladder;
-mod n0207_course_schedule;
-mod n0263_ugly_number;
-mod n0295_find_median_from_data_stream;
-mod n0148_sort_list;
-mod n0257_binary_tree_paths;
-mod n0120_triangle;
-mod n0309_best_time_to_buy_and_sell_stock_with_cooldown;
-mod n0074_search_a_2d_matrix;
-mod n0215_kth_largest_element_in_an_array;
-mod n0203_remove_linked_list_elements;
-mod n0081_search_in_rotated_sorted_array_ii;
-mod n0059_spiral_matrix_ii;
-mod n0151_reverse_words_in_a_string;
-mod n0205_isomorphic_strings;
-mod n0179_largest_number;
-mod n0168_excel_sheet_column_title;
-mod n0007_reverse_integer;
-mod n0032_longest_valid_parentheses;
-mod n0165_compare_version_numbers;
-mod n0031_next_permutation;
-mod n0088_merge_sorted_array;
-mod n0509_fibonacci_number;
-mod n0036_valid_sudoku;
-mod n0069_sqrtx;
-mod n0211_add_and_search_word_data_structure_design;
-mod n0114_flatten_binary_tree_to_linked_list;
-mod n0224_basic_calculator;
-mod n0045_jump_game_ii;
-mod n0051_n_queens;
-mod n0212_word_search_ii;
-mod n0287_find_the_duplicate_number;
-mod n0153_find_minimum_in_rotated_sorted_array;
-mod n0289_game_of_life;
-mod n0200_number_of_islands;
-mod n0015_3sum;
-mod n0216_combination_sum_iii;
-mod n0043_multiply_strings;
-mod n0090_subsets_ii;
-mod n0003_longest_substring;
-mod n0139_word_break;
-mod n0150_evaluate_reverse_polish_notation;
-mod n0063_unique_paths_ii;
-mod n0062_unique_paths;
-mod n0199_binary_tree_right_side_view;
-mod n0282_expression_add_operators;
-mod n0021_merge_two_sorted_lists;
-mod n0129_sum_root_to_leaf_numbers;
-mod n0206_reverse_linked_list;
-mod n0131_palindrome_partitioning;
-mod n0307_range_sum_query_mutable;
-mod n0111_minimum_depth_of_binary_tree;
-mod n0092_reverse_linked_list_ii;
-mod n0303_range_sum_query_immutable;
-mod n0102_binary_tree_level_order_traversal;
+pub mod solution;
+pub mod problem;
diff --git a/src/main.rs b/src/main.rs
index 967c5f8..e25be21 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,7 +3,7 @@ extern crate serde_derive;
 #[macro_use]
 extern crate serde_json;
 
-mod problem;
+mod fetcher;
 
 use std::env;
 use std::fs;
@@ -45,7 +45,7 @@ fn main() {
             }
         }
 
-        let problem = problem::get_problem(id).unwrap_or_else(|| {
+        let problem = fetcher::get_problem(id).unwrap_or_else(|| {
             panic!(
                 "Error: failed to get problem #{} \
                  (The problem may be paid-only or may not be exist).",
@@ -61,11 +61,11 @@ fn main() {
         let code = code.unwrap();
 
         let file_name = format!(
-            "n{:04}_{}",
+            "p{:04}_{}",
             problem.question_id,
             problem.title_slug.replace("-", "_")
         );
-        let file_path = Path::new("./src").join(format!("{}.rs", file_name));
+        let file_path = Path::new("./src/problem").join(format!("{}.rs", file_name));
         if file_path.exists() {
             panic!("problem already initialized");
         }
@@ -91,7 +91,7 @@ fn main() {
         let mut lib_file = fs::OpenOptions::new()
             .write(true)
             .append(true)
-            .open("./src/lib.rs")
+            .open("./src/problem/mod.rs")
             .unwrap();
         writeln!(lib_file, "mod {};", file_name);
         break;
@@ -136,13 +136,13 @@ fn parse_extra_use(code: &str) -> String {
     let mut extra_use_line = String::new();
     // a linked-list problem
     if code.contains("pub struct ListNode") {
-        extra_use_line.push_str("\nuse super::util::linked_list::{ListNode, to_list};")
+        extra_use_line.push_str("\nuse crate::util::linked_list::{ListNode, to_list};")
     }
     if code.contains("pub struct TreeNode") {
-        extra_use_line.push_str("\nuse super::util::tree::{TreeNode, to_tree};")
+        extra_use_line.push_str("\nuse crate::util::tree::{TreeNode, to_tree};")
     }
     if code.contains("pub struct Point") {
-        extra_use_line.push_str("\nuse super::util::point::Point;")
+        extra_use_line.push_str("\nuse crate::util::point::Point;")
     }
     extra_use_line
 }
diff --git a/src/problem/mod.rs b/src/problem/mod.rs
new file mode 100644
index 0000000..e69de29
diff --git a/src/solution/mod.rs b/src/solution/mod.rs
new file mode 100644
index 0000000..3b079b7
--- /dev/null
+++ b/src/solution/mod.rs
@@ -0,0 +1,237 @@
+mod s0006_zigzag_conversion;
+mod s0238_product_of_array_except_self;
+mod s0115_distinct_subsequences;
+mod s0099_recover_binary_search_tree;
+mod s0310_minimum_height_trees;
+mod s0128_longest_consecutive_sequence;
+mod s0274_h_index;
+mod s0241_different_ways_to_add_parentheses;
+mod s0024_swap_nodes_in_pairs;
+mod s0110_balanced_binary_tree;
+mod s0093_restore_ip_addresses;
+mod s0076_minimum_window_substring;
+mod s0124_binary_tree_maximum_path_sum;
+mod s0122_best_time_to_buy_and_sell_stock_ii;
+mod s0169_majority_element;
+mod s0162_find_peak_element;
+mod s0095_unique_binary_search_trees_ii;
+mod s0155_min_stack;
+mod s0040_combination_sum_ii;
+mod s0217_contains_duplicate;
+mod s0055_jump_game;
+mod s0106_construct_binary_tree_from_inorder_and_postorder_traversal;
+mod s0145_binary_tree_postorder_traversal;
+mod s0079_word_search;
+mod s0969_pancake_sorting;
+mod s0042_trapping_rain_water;
+mod s0108_convert_sorted_array_to_binary_search_tree;
+mod s0083_remove_duplicates_from_sorted_list;
+mod s0130_surrounded_regions;
+mod s0226_invert_binary_tree;
+mod s0027_remove_element;
+mod s0188_best_time_to_buy_and_sell_stock_iv;
+mod s0204_count_primes;
+mod s0268_missing_number;
+mod s0214_shortest_palindrome;
+mod s0231_power_of_two;
+mod s0202_happy_number;
+mod s0075_sort_colors;
+mod s0066_plus_one;
+mod s0028_implement_strstr;
+mod s0290_word_pattern;
+mod s0048_rotate_image;
+mod s0089_gray_code;
+mod s0147_insertion_sort_list;
+mod s0084_largest_rectangle_in_histogram;
+mod s0011_container_with_most_water;
+mod s0009_palindrome_number;
+mod s0058_length_of_last_word;
+mod s0080_remove_duplicates_from_sorted_array_ii;
+mod s0030_substring_with_concatenation_of_all_words;
+mod s0060_permutation_sequence;
+mod s0071_simplify_path;
+mod s0038_count_and_say;
+mod s0144_binary_tree_preorder_traversal;
+mod s0279_perfect_squares;
+mod s0304_range_sum_query_2d_immutable;
+mod s0292_nim_game;
+mod s0264_ugly_number_ii;
+mod s0132_palindrome_partitioning_ii;
+mod s0019_remove_nth_node_from_end_of_list;
+mod s0136_single_number;
+mod s0018_4sum;
+mod s0220_contains_duplicate_iii;
+mod s0299_bulls_and_cows;
+mod s0232_implement_queue_using_stacks;
+mod s0100_same_tree;
+mod s0171_excel_sheet_column_number;
+mod s0087_scramble_string;
+mod s0704_binary_search;
+mod s0219_contains_duplicate_ii;
+mod s0086_partition_list;
+mod s0082_remove_duplicates_from_sorted_list_ii;
+mod s0228_summary_ranges;
+mod s0020_valid_parentheses;
+mod s0017_letter_combinations_of_a_phone_number;
+mod s0312_burst_balloons;
+mod s0306_additive_number;
+mod s0283_move_zeroes;
+mod s1018_binary_prefix_divisible_by_5;
+mod s0201_bitwise_and_of_numbers_range;
+mod s0109_convert_sorted_list_to_binary_search_tree;
+mod s0101_symmetric_tree;
+mod s0098_validate_binary_search_tree;
+mod s0035_search_insert_position;
+mod s0050_powx_n;
+mod s0198_house_robber;
+mod s0004_median_of_two_sorted_arrays;
+mod s0221_maximal_square;
+mod s0047_permutations_ii;
+mod s0172_factorial_trailing_zeroes;
+mod s0054_spiral_matrix;
+mod s0053_maximum_subarray;
+mod s1046_last_stone_weight;
+mod s0146_lru_cache;
+mod s0126_word_ladder_ii;
+mod s0242_valid_anagram;
+mod s0112_path_sum;
+mod s0023_merge_k_sorted_lists;
+mod s0230_kth_smallest_element_in_a_bst;
+mod s0104_maximum_depth_of_binary_tree;
+mod s0258_add_digits;
+mod s0187_repeated_dna_sequences;
+mod s0025_reverse_nodes_in_k_group;
+mod s0039_combination_sum;
+mod s0107_binary_tree_level_order_traversal_ii;
+mod s0091_decode_ways;
+mod s0056_merge_intervals;
+mod s0065_valid_number;
+mod s0016_3sum_closest;
+mod s0096_unique_binary_search_trees;
+mod s0072_edit_distance;
+mod s0044_wildcard_matching;
+mod s0239_sliding_window_maximum;
+mod s0174_dungeon_game;
+mod s0073_set_matrix_zeroes;
+mod s0078_subsets;
+mod s0037_sudoku_solver;
+mod s0033_search_in_rotated_sorted_array;
+mod s0002_add_two_numbers;
+mod s0313_super_ugly_number;
+mod s0068_text_justification;
+mod s0064_minimum_path_sum;
+mod s0218_the_skyline_problem;
+mod s0125_valid_palindrome;
+mod s0210_course_schedule_ii;
+mod s0143_reorder_list;
+mod s0164_maximum_gap;
+mod s0097_interleaving_string;
+mod s0105_construct_binary_tree_from_preorder_and_inorder_traversal;
+mod s0167_two_sum_ii_input_array_is_sorted;
+mod s0034_find_first_and_last_position_of_element_in_sorted_array;
+mod s0094_binary_tree_inorder_traversal;
+mod s0052_n_queens_ii;
+mod s0121_best_time_to_buy_and_sell_stock;
+mod s0273_integer_to_english_words;
+mod s0225_implement_stack_using_queues;
+mod s0046_permutations;
+mod s0085_maximal_rectangle;
+mod s0135_candy;
+mod s0113_path_sum_ii;
+mod s0029_divide_two_integers;
+mod s0260_single_number_iii;
+mod s0140_word_break_ii;
+mod s0149_max_points_on_a_line;
+mod s0213_house_robber_ii;
+mod s0222_count_complete_tree_nodes;
+mod s0134_gas_station;
+mod s0057_insert_interval;
+mod s0173_binary_search_tree_iterator;
+mod s0077_combinations;
+mod s0005_longest_palindromic_substring;
+mod s0041_first_missing_positive;
+mod s0026_remove_duplicates_from_sorted_array;
+mod s0166_fraction_to_recurring_decimal;
+mod s0119_pascals_triangle_ii;
+mod s0012_integer_to_roman;
+mod s0223_rectangle_area;
+mod s0229_majority_element_ii;
+mod s0061_rotate_list;
+mod s0123_best_time_to_buy_and_sell_stock_iii;
+mod s0301_remove_invalid_parentheses;
+mod s0067_add_binary;
+mod s0049_group_anagrams;
+mod s0189_rotate_array;
+mod s0001_two_sum;
+mod s0275_h_index_ii;
+mod s0103_binary_tree_zigzag_level_order_traversal;
+mod s0137_single_number_ii;
+mod s0208_implement_trie_prefix_tree;
+mod s0300_longest_increasing_subsequence;
+mod s0118_pascals_triangle;
+mod s0010_regular_expression_matching;
+mod s0013_roman_to_integer;
+mod s0209_minimum_size_subarray_sum;
+mod s0227_basic_calculator_ii;
+mod s0022_generate_parentheses;
+mod s0008_string_to_integer_atoi;
+mod s0152_maximum_product_subarray;
+mod s0014_longest_common_prefix;
+mod s0070_climbing_stairs;
+mod s0233_number_of_digit_one;
+mod s0154_find_minimum_in_rotated_sorted_array_ii;
+mod s0127_word_ladder;
+mod s0207_course_schedule;
+mod s0263_ugly_number;
+mod s0295_find_median_from_data_stream;
+mod s0148_sort_list;
+mod s0257_binary_tree_paths;
+mod s0120_triangle;
+mod s0309_best_time_to_buy_and_sell_stock_with_cooldown;
+mod s0074_search_a_2d_matrix;
+mod s0215_kth_largest_element_in_an_array;
+mod s0203_remove_linked_list_elements;
+mod s0081_search_in_rotated_sorted_array_ii;
+mod s0059_spiral_matrix_ii;
+mod s0151_reverse_words_in_a_string;
+mod s0205_isomorphic_strings;
+mod s0179_largest_number;
+mod s0168_excel_sheet_column_title;
+mod s0007_reverse_integer;
+mod s0032_longest_valid_parentheses;
+mod s0165_compare_version_numbers;
+mod s0031_next_permutation;
+mod s0088_merge_sorted_array;
+mod s0509_fibonacci_number;
+mod s0036_valid_sudoku;
+mod s0069_sqrtx;
+mod s0211_add_and_search_word_data_structure_design;
+mod s0114_flatten_binary_tree_to_linked_list;
+mod s0224_basic_calculator;
+mod s0045_jump_game_ii;
+mod s0051_n_queens;
+mod s0212_word_search_ii;
+mod s0287_find_the_duplicate_number;
+mod s0153_find_minimum_in_rotated_sorted_array;
+mod s0289_game_of_life;
+mod s0200_number_of_islands;
+mod s0015_3sum;
+mod s0216_combination_sum_iii;
+mod s0043_multiply_strings;
+mod s0090_subsets_ii;
+mod s0003_longest_substring;
+mod s0139_word_break;
+mod s0150_evaluate_reverse_polish_notation;
+mod s0063_unique_paths_ii;
+mod s0062_unique_paths;
+mod s0199_binary_tree_right_side_view;
+mod s0282_expression_add_operators;
+mod s0021_merge_two_sorted_lists;
+mod s0129_sum_root_to_leaf_numbers;
+mod s0206_reverse_linked_list;
+mod s0131_palindrome_partitioning;
+mod s0307_range_sum_query_mutable;
+mod s0111_minimum_depth_of_binary_tree;
+mod s0092_reverse_linked_list_ii;
+mod s0303_range_sum_query_immutable;
+mod s0102_binary_tree_level_order_traversal;
diff --git a/src/n0001_two_sum.rs b/src/solution/s0001_two_sum.rs
similarity index 100%
rename from src/n0001_two_sum.rs
rename to src/solution/s0001_two_sum.rs
diff --git a/src/n0002_add_two_numbers.rs b/src/solution/s0002_add_two_numbers.rs
similarity index 98%
rename from src/n0002_add_two_numbers.rs
rename to src/solution/s0002_add_two_numbers.rs
index b7b21b0..5612c3d 100644
--- a/src/n0002_add_two_numbers.rs
+++ b/src/solution/s0002_add_two_numbers.rs
@@ -17,7 +17,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0003_longest_substring.rs b/src/solution/s0003_longest_substring.rs
similarity index 100%
rename from src/n0003_longest_substring.rs
rename to src/solution/s0003_longest_substring.rs
diff --git a/src/n0004_median_of_two_sorted_arrays.rs b/src/solution/s0004_median_of_two_sorted_arrays.rs
similarity index 100%
rename from src/n0004_median_of_two_sorted_arrays.rs
rename to src/solution/s0004_median_of_two_sorted_arrays.rs
diff --git a/src/n0005_longest_palindromic_substring.rs b/src/solution/s0005_longest_palindromic_substring.rs
similarity index 100%
rename from src/n0005_longest_palindromic_substring.rs
rename to src/solution/s0005_longest_palindromic_substring.rs
diff --git a/src/n0006_zigzag_conversion.rs b/src/solution/s0006_zigzag_conversion.rs
similarity index 100%
rename from src/n0006_zigzag_conversion.rs
rename to src/solution/s0006_zigzag_conversion.rs
diff --git a/src/n0007_reverse_integer.rs b/src/solution/s0007_reverse_integer.rs
similarity index 100%
rename from src/n0007_reverse_integer.rs
rename to src/solution/s0007_reverse_integer.rs
diff --git a/src/n0008_string_to_integer_atoi.rs b/src/solution/s0008_string_to_integer_atoi.rs
similarity index 100%
rename from src/n0008_string_to_integer_atoi.rs
rename to src/solution/s0008_string_to_integer_atoi.rs
diff --git a/src/n0009_palindrome_number.rs b/src/solution/s0009_palindrome_number.rs
similarity index 100%
rename from src/n0009_palindrome_number.rs
rename to src/solution/s0009_palindrome_number.rs
diff --git a/src/n0010_regular_expression_matching.rs b/src/solution/s0010_regular_expression_matching.rs
similarity index 100%
rename from src/n0010_regular_expression_matching.rs
rename to src/solution/s0010_regular_expression_matching.rs
diff --git a/src/n0011_container_with_most_water.rs b/src/solution/s0011_container_with_most_water.rs
similarity index 100%
rename from src/n0011_container_with_most_water.rs
rename to src/solution/s0011_container_with_most_water.rs
diff --git a/src/n0012_integer_to_roman.rs b/src/solution/s0012_integer_to_roman.rs
similarity index 100%
rename from src/n0012_integer_to_roman.rs
rename to src/solution/s0012_integer_to_roman.rs
diff --git a/src/n0013_roman_to_integer.rs b/src/solution/s0013_roman_to_integer.rs
similarity index 100%
rename from src/n0013_roman_to_integer.rs
rename to src/solution/s0013_roman_to_integer.rs
diff --git a/src/n0014_longest_common_prefix.rs b/src/solution/s0014_longest_common_prefix.rs
similarity index 100%
rename from src/n0014_longest_common_prefix.rs
rename to src/solution/s0014_longest_common_prefix.rs
diff --git a/src/n0015_3sum.rs b/src/solution/s0015_3sum.rs
similarity index 100%
rename from src/n0015_3sum.rs
rename to src/solution/s0015_3sum.rs
diff --git a/src/n0016_3sum_closest.rs b/src/solution/s0016_3sum_closest.rs
similarity index 100%
rename from src/n0016_3sum_closest.rs
rename to src/solution/s0016_3sum_closest.rs
diff --git a/src/n0017_letter_combinations_of_a_phone_number.rs b/src/solution/s0017_letter_combinations_of_a_phone_number.rs
similarity index 100%
rename from src/n0017_letter_combinations_of_a_phone_number.rs
rename to src/solution/s0017_letter_combinations_of_a_phone_number.rs
diff --git a/src/n0018_4sum.rs b/src/solution/s0018_4sum.rs
similarity index 100%
rename from src/n0018_4sum.rs
rename to src/solution/s0018_4sum.rs
diff --git a/src/n0019_remove_nth_node_from_end_of_list.rs b/src/solution/s0019_remove_nth_node_from_end_of_list.rs
similarity index 97%
rename from src/n0019_remove_nth_node_from_end_of_list.rs
rename to src/solution/s0019_remove_nth_node_from_end_of_list.rs
index a1698a4..b3dac82 100644
--- a/src/n0019_remove_nth_node_from_end_of_list.rs
+++ b/src/solution/s0019_remove_nth_node_from_end_of_list.rs
@@ -21,7 +21,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0020_valid_parentheses.rs b/src/solution/s0020_valid_parentheses.rs
similarity index 100%
rename from src/n0020_valid_parentheses.rs
rename to src/solution/s0020_valid_parentheses.rs
diff --git a/src/n0021_merge_two_sorted_lists.rs b/src/solution/s0021_merge_two_sorted_lists.rs
similarity index 97%
rename from src/n0021_merge_two_sorted_lists.rs
rename to src/solution/s0021_merge_two_sorted_lists.rs
index 5a25adf..c496d8e 100644
--- a/src/n0021_merge_two_sorted_lists.rs
+++ b/src/solution/s0021_merge_two_sorted_lists.rs
@@ -11,7 +11,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0022_generate_parentheses.rs b/src/solution/s0022_generate_parentheses.rs
similarity index 100%
rename from src/n0022_generate_parentheses.rs
rename to src/solution/s0022_generate_parentheses.rs
diff --git a/src/n0023_merge_k_sorted_lists.rs b/src/solution/s0023_merge_k_sorted_lists.rs
similarity index 97%
rename from src/n0023_merge_k_sorted_lists.rs
rename to src/solution/s0023_merge_k_sorted_lists.rs
index 74b9504..c213eb7 100644
--- a/src/n0023_merge_k_sorted_lists.rs
+++ b/src/solution/s0023_merge_k_sorted_lists.rs
@@ -17,7 +17,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 use std::cmp::Ordering;
diff --git a/src/n0024_swap_nodes_in_pairs.rs b/src/solution/s0024_swap_nodes_in_pairs.rs
similarity index 97%
rename from src/n0024_swap_nodes_in_pairs.rs
rename to src/solution/s0024_swap_nodes_in_pairs.rs
index 41e3c6c..104d6b9 100644
--- a/src/n0024_swap_nodes_in_pairs.rs
+++ b/src/solution/s0024_swap_nodes_in_pairs.rs
@@ -17,7 +17,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0025_reverse_nodes_in_k_group.rs b/src/solution/s0025_reverse_nodes_in_k_group.rs
similarity index 98%
rename from src/n0025_reverse_nodes_in_k_group.rs
rename to src/solution/s0025_reverse_nodes_in_k_group.rs
index aac987f..3beb552 100644
--- a/src/n0025_reverse_nodes_in_k_group.rs
+++ b/src/solution/s0025_reverse_nodes_in_k_group.rs
@@ -25,7 +25,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0026_remove_duplicates_from_sorted_array.rs b/src/solution/s0026_remove_duplicates_from_sorted_array.rs
similarity index 100%
rename from src/n0026_remove_duplicates_from_sorted_array.rs
rename to src/solution/s0026_remove_duplicates_from_sorted_array.rs
diff --git a/src/n0027_remove_element.rs b/src/solution/s0027_remove_element.rs
similarity index 100%
rename from src/n0027_remove_element.rs
rename to src/solution/s0027_remove_element.rs
diff --git a/src/n0028_implement_strstr.rs b/src/solution/s0028_implement_strstr.rs
similarity index 100%
rename from src/n0028_implement_strstr.rs
rename to src/solution/s0028_implement_strstr.rs
diff --git a/src/n0029_divide_two_integers.rs b/src/solution/s0029_divide_two_integers.rs
similarity index 100%
rename from src/n0029_divide_two_integers.rs
rename to src/solution/s0029_divide_two_integers.rs
diff --git a/src/n0030_substring_with_concatenation_of_all_words.rs b/src/solution/s0030_substring_with_concatenation_of_all_words.rs
similarity index 100%
rename from src/n0030_substring_with_concatenation_of_all_words.rs
rename to src/solution/s0030_substring_with_concatenation_of_all_words.rs
diff --git a/src/n0031_next_permutation.rs b/src/solution/s0031_next_permutation.rs
similarity index 100%
rename from src/n0031_next_permutation.rs
rename to src/solution/s0031_next_permutation.rs
diff --git a/src/n0032_longest_valid_parentheses.rs b/src/solution/s0032_longest_valid_parentheses.rs
similarity index 100%
rename from src/n0032_longest_valid_parentheses.rs
rename to src/solution/s0032_longest_valid_parentheses.rs
diff --git a/src/n0033_search_in_rotated_sorted_array.rs b/src/solution/s0033_search_in_rotated_sorted_array.rs
similarity index 100%
rename from src/n0033_search_in_rotated_sorted_array.rs
rename to src/solution/s0033_search_in_rotated_sorted_array.rs
diff --git a/src/n0034_find_first_and_last_position_of_element_in_sorted_array.rs b/src/solution/s0034_find_first_and_last_position_of_element_in_sorted_array.rs
similarity index 100%
rename from src/n0034_find_first_and_last_position_of_element_in_sorted_array.rs
rename to src/solution/s0034_find_first_and_last_position_of_element_in_sorted_array.rs
diff --git a/src/n0035_search_insert_position.rs b/src/solution/s0035_search_insert_position.rs
similarity index 100%
rename from src/n0035_search_insert_position.rs
rename to src/solution/s0035_search_insert_position.rs
diff --git a/src/n0036_valid_sudoku.rs b/src/solution/s0036_valid_sudoku.rs
similarity index 100%
rename from src/n0036_valid_sudoku.rs
rename to src/solution/s0036_valid_sudoku.rs
diff --git a/src/n0037_sudoku_solver.rs b/src/solution/s0037_sudoku_solver.rs
similarity index 100%
rename from src/n0037_sudoku_solver.rs
rename to src/solution/s0037_sudoku_solver.rs
diff --git a/src/n0038_count_and_say.rs b/src/solution/s0038_count_and_say.rs
similarity index 100%
rename from src/n0038_count_and_say.rs
rename to src/solution/s0038_count_and_say.rs
diff --git a/src/n0039_combination_sum.rs b/src/solution/s0039_combination_sum.rs
similarity index 100%
rename from src/n0039_combination_sum.rs
rename to src/solution/s0039_combination_sum.rs
diff --git a/src/n0040_combination_sum_ii.rs b/src/solution/s0040_combination_sum_ii.rs
similarity index 100%
rename from src/n0040_combination_sum_ii.rs
rename to src/solution/s0040_combination_sum_ii.rs
diff --git a/src/n0041_first_missing_positive.rs b/src/solution/s0041_first_missing_positive.rs
similarity index 100%
rename from src/n0041_first_missing_positive.rs
rename to src/solution/s0041_first_missing_positive.rs
diff --git a/src/n0042_trapping_rain_water.rs b/src/solution/s0042_trapping_rain_water.rs
similarity index 100%
rename from src/n0042_trapping_rain_water.rs
rename to src/solution/s0042_trapping_rain_water.rs
diff --git a/src/n0043_multiply_strings.rs b/src/solution/s0043_multiply_strings.rs
similarity index 100%
rename from src/n0043_multiply_strings.rs
rename to src/solution/s0043_multiply_strings.rs
diff --git a/src/n0044_wildcard_matching.rs b/src/solution/s0044_wildcard_matching.rs
similarity index 100%
rename from src/n0044_wildcard_matching.rs
rename to src/solution/s0044_wildcard_matching.rs
diff --git a/src/n0045_jump_game_ii.rs b/src/solution/s0045_jump_game_ii.rs
similarity index 100%
rename from src/n0045_jump_game_ii.rs
rename to src/solution/s0045_jump_game_ii.rs
diff --git a/src/n0046_permutations.rs b/src/solution/s0046_permutations.rs
similarity index 100%
rename from src/n0046_permutations.rs
rename to src/solution/s0046_permutations.rs
diff --git a/src/n0047_permutations_ii.rs b/src/solution/s0047_permutations_ii.rs
similarity index 100%
rename from src/n0047_permutations_ii.rs
rename to src/solution/s0047_permutations_ii.rs
diff --git a/src/n0048_rotate_image.rs b/src/solution/s0048_rotate_image.rs
similarity index 100%
rename from src/n0048_rotate_image.rs
rename to src/solution/s0048_rotate_image.rs
diff --git a/src/n0049_group_anagrams.rs b/src/solution/s0049_group_anagrams.rs
similarity index 100%
rename from src/n0049_group_anagrams.rs
rename to src/solution/s0049_group_anagrams.rs
diff --git a/src/n0050_powx_n.rs b/src/solution/s0050_powx_n.rs
similarity index 100%
rename from src/n0050_powx_n.rs
rename to src/solution/s0050_powx_n.rs
diff --git a/src/n0051_n_queens.rs b/src/solution/s0051_n_queens.rs
similarity index 100%
rename from src/n0051_n_queens.rs
rename to src/solution/s0051_n_queens.rs
diff --git a/src/n0052_n_queens_ii.rs b/src/solution/s0052_n_queens_ii.rs
similarity index 100%
rename from src/n0052_n_queens_ii.rs
rename to src/solution/s0052_n_queens_ii.rs
diff --git a/src/n0053_maximum_subarray.rs b/src/solution/s0053_maximum_subarray.rs
similarity index 100%
rename from src/n0053_maximum_subarray.rs
rename to src/solution/s0053_maximum_subarray.rs
diff --git a/src/n0054_spiral_matrix.rs b/src/solution/s0054_spiral_matrix.rs
similarity index 100%
rename from src/n0054_spiral_matrix.rs
rename to src/solution/s0054_spiral_matrix.rs
diff --git a/src/n0055_jump_game.rs b/src/solution/s0055_jump_game.rs
similarity index 100%
rename from src/n0055_jump_game.rs
rename to src/solution/s0055_jump_game.rs
diff --git a/src/n0056_merge_intervals.rs b/src/solution/s0056_merge_intervals.rs
similarity index 100%
rename from src/n0056_merge_intervals.rs
rename to src/solution/s0056_merge_intervals.rs
diff --git a/src/n0057_insert_interval.rs b/src/solution/s0057_insert_interval.rs
similarity index 100%
rename from src/n0057_insert_interval.rs
rename to src/solution/s0057_insert_interval.rs
diff --git a/src/n0058_length_of_last_word.rs b/src/solution/s0058_length_of_last_word.rs
similarity index 100%
rename from src/n0058_length_of_last_word.rs
rename to src/solution/s0058_length_of_last_word.rs
diff --git a/src/n0059_spiral_matrix_ii.rs b/src/solution/s0059_spiral_matrix_ii.rs
similarity index 100%
rename from src/n0059_spiral_matrix_ii.rs
rename to src/solution/s0059_spiral_matrix_ii.rs
diff --git a/src/n0060_permutation_sequence.rs b/src/solution/s0060_permutation_sequence.rs
similarity index 100%
rename from src/n0060_permutation_sequence.rs
rename to src/solution/s0060_permutation_sequence.rs
diff --git a/src/n0061_rotate_list.rs b/src/solution/s0061_rotate_list.rs
similarity index 94%
rename from src/n0061_rotate_list.rs
rename to src/solution/s0061_rotate_list.rs
index 0881211..b772357 100644
--- a/src/n0061_rotate_list.rs
+++ b/src/solution/s0061_rotate_list.rs
@@ -26,7 +26,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0062_unique_paths.rs b/src/solution/s0062_unique_paths.rs
similarity index 100%
rename from src/n0062_unique_paths.rs
rename to src/solution/s0062_unique_paths.rs
diff --git a/src/n0063_unique_paths_ii.rs b/src/solution/s0063_unique_paths_ii.rs
similarity index 100%
rename from src/n0063_unique_paths_ii.rs
rename to src/solution/s0063_unique_paths_ii.rs
diff --git a/src/n0064_minimum_path_sum.rs b/src/solution/s0064_minimum_path_sum.rs
similarity index 100%
rename from src/n0064_minimum_path_sum.rs
rename to src/solution/s0064_minimum_path_sum.rs
diff --git a/src/n0065_valid_number.rs b/src/solution/s0065_valid_number.rs
similarity index 100%
rename from src/n0065_valid_number.rs
rename to src/solution/s0065_valid_number.rs
diff --git a/src/n0066_plus_one.rs b/src/solution/s0066_plus_one.rs
similarity index 100%
rename from src/n0066_plus_one.rs
rename to src/solution/s0066_plus_one.rs
diff --git a/src/n0067_add_binary.rs b/src/solution/s0067_add_binary.rs
similarity index 100%
rename from src/n0067_add_binary.rs
rename to src/solution/s0067_add_binary.rs
diff --git a/src/n0068_text_justification.rs b/src/solution/s0068_text_justification.rs
similarity index 100%
rename from src/n0068_text_justification.rs
rename to src/solution/s0068_text_justification.rs
diff --git a/src/n0069_sqrtx.rs b/src/solution/s0069_sqrtx.rs
similarity index 100%
rename from src/n0069_sqrtx.rs
rename to src/solution/s0069_sqrtx.rs
diff --git a/src/n0070_climbing_stairs.rs b/src/solution/s0070_climbing_stairs.rs
similarity index 100%
rename from src/n0070_climbing_stairs.rs
rename to src/solution/s0070_climbing_stairs.rs
diff --git a/src/n0071_simplify_path.rs b/src/solution/s0071_simplify_path.rs
similarity index 100%
rename from src/n0071_simplify_path.rs
rename to src/solution/s0071_simplify_path.rs
diff --git a/src/n0072_edit_distance.rs b/src/solution/s0072_edit_distance.rs
similarity index 100%
rename from src/n0072_edit_distance.rs
rename to src/solution/s0072_edit_distance.rs
diff --git a/src/n0073_set_matrix_zeroes.rs b/src/solution/s0073_set_matrix_zeroes.rs
similarity index 100%
rename from src/n0073_set_matrix_zeroes.rs
rename to src/solution/s0073_set_matrix_zeroes.rs
diff --git a/src/n0074_search_a_2d_matrix.rs b/src/solution/s0074_search_a_2d_matrix.rs
similarity index 100%
rename from src/n0074_search_a_2d_matrix.rs
rename to src/solution/s0074_search_a_2d_matrix.rs
diff --git a/src/n0075_sort_colors.rs b/src/solution/s0075_sort_colors.rs
similarity index 100%
rename from src/n0075_sort_colors.rs
rename to src/solution/s0075_sort_colors.rs
diff --git a/src/n0076_minimum_window_substring.rs b/src/solution/s0076_minimum_window_substring.rs
similarity index 100%
rename from src/n0076_minimum_window_substring.rs
rename to src/solution/s0076_minimum_window_substring.rs
diff --git a/src/n0077_combinations.rs b/src/solution/s0077_combinations.rs
similarity index 100%
rename from src/n0077_combinations.rs
rename to src/solution/s0077_combinations.rs
diff --git a/src/n0078_subsets.rs b/src/solution/s0078_subsets.rs
similarity index 100%
rename from src/n0078_subsets.rs
rename to src/solution/s0078_subsets.rs
diff --git a/src/n0079_word_search.rs b/src/solution/s0079_word_search.rs
similarity index 100%
rename from src/n0079_word_search.rs
rename to src/solution/s0079_word_search.rs
diff --git a/src/n0080_remove_duplicates_from_sorted_array_ii.rs b/src/solution/s0080_remove_duplicates_from_sorted_array_ii.rs
similarity index 100%
rename from src/n0080_remove_duplicates_from_sorted_array_ii.rs
rename to src/solution/s0080_remove_duplicates_from_sorted_array_ii.rs
diff --git a/src/n0081_search_in_rotated_sorted_array_ii.rs b/src/solution/s0081_search_in_rotated_sorted_array_ii.rs
similarity index 100%
rename from src/n0081_search_in_rotated_sorted_array_ii.rs
rename to src/solution/s0081_search_in_rotated_sorted_array_ii.rs
diff --git a/src/n0082_remove_duplicates_from_sorted_list_ii.rs b/src/solution/s0082_remove_duplicates_from_sorted_list_ii.rs
similarity index 94%
rename from src/n0082_remove_duplicates_from_sorted_list_ii.rs
rename to src/solution/s0082_remove_duplicates_from_sorted_list_ii.rs
index ff8c8b8..d04b15f 100644
--- a/src/n0082_remove_duplicates_from_sorted_list_ii.rs
+++ b/src/solution/s0082_remove_duplicates_from_sorted_list_ii.rs
@@ -19,7 +19,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0083_remove_duplicates_from_sorted_list.rs b/src/solution/s0083_remove_duplicates_from_sorted_list.rs
similarity index 94%
rename from src/n0083_remove_duplicates_from_sorted_list.rs
rename to src/solution/s0083_remove_duplicates_from_sorted_list.rs
index b8fa539..785cc03 100644
--- a/src/n0083_remove_duplicates_from_sorted_list.rs
+++ b/src/solution/s0083_remove_duplicates_from_sorted_list.rs
@@ -19,7 +19,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0084_largest_rectangle_in_histogram.rs b/src/solution/s0084_largest_rectangle_in_histogram.rs
similarity index 100%
rename from src/n0084_largest_rectangle_in_histogram.rs
rename to src/solution/s0084_largest_rectangle_in_histogram.rs
diff --git a/src/n0085_maximal_rectangle.rs b/src/solution/s0085_maximal_rectangle.rs
similarity index 100%
rename from src/n0085_maximal_rectangle.rs
rename to src/solution/s0085_maximal_rectangle.rs
diff --git a/src/n0086_partition_list.rs b/src/solution/s0086_partition_list.rs
similarity index 97%
rename from src/n0086_partition_list.rs
rename to src/solution/s0086_partition_list.rs
index ad03b08..4238586 100644
--- a/src/n0086_partition_list.rs
+++ b/src/solution/s0086_partition_list.rs
@@ -14,7 +14,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 impl Solution {
     pub fn partition(head: Option<Box<ListNode>>, x: i32) -> Option<Box<ListNode>> {
diff --git a/src/n0087_scramble_string.rs b/src/solution/s0087_scramble_string.rs
similarity index 100%
rename from src/n0087_scramble_string.rs
rename to src/solution/s0087_scramble_string.rs
diff --git a/src/n0088_merge_sorted_array.rs b/src/solution/s0088_merge_sorted_array.rs
similarity index 100%
rename from src/n0088_merge_sorted_array.rs
rename to src/solution/s0088_merge_sorted_array.rs
diff --git a/src/n0089_gray_code.rs b/src/solution/s0089_gray_code.rs
similarity index 100%
rename from src/n0089_gray_code.rs
rename to src/solution/s0089_gray_code.rs
diff --git a/src/n0090_subsets_ii.rs b/src/solution/s0090_subsets_ii.rs
similarity index 100%
rename from src/n0090_subsets_ii.rs
rename to src/solution/s0090_subsets_ii.rs
diff --git a/src/n0091_decode_ways.rs b/src/solution/s0091_decode_ways.rs
similarity index 100%
rename from src/n0091_decode_ways.rs
rename to src/solution/s0091_decode_ways.rs
diff --git a/src/n0092_reverse_linked_list_ii.rs b/src/solution/s0092_reverse_linked_list_ii.rs
similarity index 94%
rename from src/n0092_reverse_linked_list_ii.rs
rename to src/solution/s0092_reverse_linked_list_ii.rs
index 705a787..e84035d 100644
--- a/src/n0092_reverse_linked_list_ii.rs
+++ b/src/solution/s0092_reverse_linked_list_ii.rs
@@ -14,7 +14,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0093_restore_ip_addresses.rs b/src/solution/s0093_restore_ip_addresses.rs
similarity index 100%
rename from src/n0093_restore_ip_addresses.rs
rename to src/solution/s0093_restore_ip_addresses.rs
diff --git a/src/n0094_binary_tree_inorder_traversal.rs b/src/solution/s0094_binary_tree_inorder_traversal.rs
similarity index 96%
rename from src/n0094_binary_tree_inorder_traversal.rs
rename to src/solution/s0094_binary_tree_inorder_traversal.rs
index c40cd1c..d4d2ea2 100644
--- a/src/n0094_binary_tree_inorder_traversal.rs
+++ b/src/solution/s0094_binary_tree_inorder_traversal.rs
@@ -22,7 +22,7 @@ pub struct Solution {}
 
 // submission codes start here
 
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 use std::cell::RefCell;
 use std::rc::Rc;
 impl Solution {
diff --git a/src/n0095_unique_binary_search_trees_ii.rs b/src/solution/s0095_unique_binary_search_trees_ii.rs
similarity index 97%
rename from src/n0095_unique_binary_search_trees_ii.rs
rename to src/solution/s0095_unique_binary_search_trees_ii.rs
index 3ab366e..ffdc763 100644
--- a/src/n0095_unique_binary_search_trees_ii.rs
+++ b/src/solution/s0095_unique_binary_search_trees_ii.rs
@@ -48,7 +48,7 @@ pub struct Solution {}
       / \
      2   4
  */
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 use std::cell::RefCell;
 use std::rc::Rc;
 impl Solution {
diff --git a/src/n0096_unique_binary_search_trees.rs b/src/solution/s0096_unique_binary_search_trees.rs
similarity index 100%
rename from src/n0096_unique_binary_search_trees.rs
rename to src/solution/s0096_unique_binary_search_trees.rs
diff --git a/src/n0097_interleaving_string.rs b/src/solution/s0097_interleaving_string.rs
similarity index 100%
rename from src/n0097_interleaving_string.rs
rename to src/solution/s0097_interleaving_string.rs
diff --git a/src/n0098_validate_binary_search_tree.rs b/src/solution/s0098_validate_binary_search_tree.rs
similarity index 98%
rename from src/n0098_validate_binary_search_tree.rs
rename to src/solution/s0098_validate_binary_search_tree.rs
index fcb359e..7f55a47 100644
--- a/src/n0098_validate_binary_search_tree.rs
+++ b/src/solution/s0098_validate_binary_search_tree.rs
@@ -40,7 +40,7 @@ pub struct Solution {}
 // submission codes start here
 
 // Definition for a binary tree node.
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 use std::cell::RefCell;
 use std::rc::Rc;
diff --git a/src/n0099_recover_binary_search_tree.rs b/src/solution/s0099_recover_binary_search_tree.rs
similarity index 95%
rename from src/n0099_recover_binary_search_tree.rs
rename to src/solution/s0099_recover_binary_search_tree.rs
index 8bc39b3..3b92da0 100644
--- a/src/n0099_recover_binary_search_tree.rs
+++ b/src/solution/s0099_recover_binary_search_tree.rs
@@ -55,7 +55,7 @@
  */
 pub struct Solution {}
 
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0100_same_tree.rs b/src/solution/s0100_same_tree.rs
similarity index 96%
rename from src/n0100_same_tree.rs
rename to src/solution/s0100_same_tree.rs
index 51b7ad7..f1ca197 100644
--- a/src/n0100_same_tree.rs
+++ b/src/solution/s0100_same_tree.rs
@@ -44,7 +44,7 @@
  */
 pub struct Solution {}
 
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 // submission codes start here
 use std::cell::RefCell;
 use std::rc::Rc;
diff --git a/src/n0101_symmetric_tree.rs b/src/solution/s0101_symmetric_tree.rs
similarity index 97%
rename from src/n0101_symmetric_tree.rs
rename to src/solution/s0101_symmetric_tree.rs
index d341ff3..c62962d 100644
--- a/src/n0101_symmetric_tree.rs
+++ b/src/solution/s0101_symmetric_tree.rs
@@ -30,7 +30,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0102_binary_tree_level_order_traversal.rs b/src/solution/s0102_binary_tree_level_order_traversal.rs
similarity index 97%
rename from src/n0102_binary_tree_level_order_traversal.rs
rename to src/solution/s0102_binary_tree_level_order_traversal.rs
index 6fdabf6..42f782a 100644
--- a/src/n0102_binary_tree_level_order_traversal.rs
+++ b/src/solution/s0102_binary_tree_level_order_traversal.rs
@@ -26,7 +26,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0103_binary_tree_zigzag_level_order_traversal.rs b/src/solution/s0103_binary_tree_zigzag_level_order_traversal.rs
similarity index 97%
rename from src/n0103_binary_tree_zigzag_level_order_traversal.rs
rename to src/solution/s0103_binary_tree_zigzag_level_order_traversal.rs
index ce31b6b..96476fd 100644
--- a/src/n0103_binary_tree_zigzag_level_order_traversal.rs
+++ b/src/solution/s0103_binary_tree_zigzag_level_order_traversal.rs
@@ -26,7 +26,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0104_maximum_depth_of_binary_tree.rs b/src/solution/s0104_maximum_depth_of_binary_tree.rs
similarity index 96%
rename from src/n0104_maximum_depth_of_binary_tree.rs
rename to src/solution/s0104_maximum_depth_of_binary_tree.rs
index c5faf23..6d2f18e 100644
--- a/src/n0104_maximum_depth_of_binary_tree.rs
+++ b/src/solution/s0104_maximum_depth_of_binary_tree.rs
@@ -22,7 +22,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0105_construct_binary_tree_from_preorder_and_inorder_traversal.rs b/src/solution/s0105_construct_binary_tree_from_preorder_and_inorder_traversal.rs
similarity index 97%
rename from src/n0105_construct_binary_tree_from_preorder_and_inorder_traversal.rs
rename to src/solution/s0105_construct_binary_tree_from_preorder_and_inorder_traversal.rs
index 611725d..e271faa 100644
--- a/src/n0105_construct_binary_tree_from_preorder_and_inorder_traversal.rs
+++ b/src/solution/s0105_construct_binary_tree_from_preorder_and_inorder_traversal.rs
@@ -23,7 +23,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0106_construct_binary_tree_from_inorder_and_postorder_traversal.rs b/src/solution/s0106_construct_binary_tree_from_inorder_and_postorder_traversal.rs
similarity index 97%
rename from src/n0106_construct_binary_tree_from_inorder_and_postorder_traversal.rs
rename to src/solution/s0106_construct_binary_tree_from_inorder_and_postorder_traversal.rs
index 7d3e820..63c469b 100644
--- a/src/n0106_construct_binary_tree_from_inorder_and_postorder_traversal.rs
+++ b/src/solution/s0106_construct_binary_tree_from_inorder_and_postorder_traversal.rs
@@ -24,7 +24,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0107_binary_tree_level_order_traversal_ii.rs b/src/solution/s0107_binary_tree_level_order_traversal_ii.rs
similarity index 97%
rename from src/n0107_binary_tree_level_order_traversal_ii.rs
rename to src/solution/s0107_binary_tree_level_order_traversal_ii.rs
index 4285596..f77229a 100644
--- a/src/n0107_binary_tree_level_order_traversal_ii.rs
+++ b/src/solution/s0107_binary_tree_level_order_traversal_ii.rs
@@ -26,7 +26,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0108_convert_sorted_array_to_binary_search_tree.rs b/src/solution/s0108_convert_sorted_array_to_binary_search_tree.rs
similarity index 97%
rename from src/n0108_convert_sorted_array_to_binary_search_tree.rs
rename to src/solution/s0108_convert_sorted_array_to_binary_search_tree.rs
index 4da3378..67e4b2a 100644
--- a/src/n0108_convert_sorted_array_to_binary_search_tree.rs
+++ b/src/solution/s0108_convert_sorted_array_to_binary_search_tree.rs
@@ -21,7 +21,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0109_convert_sorted_list_to_binary_search_tree.rs b/src/solution/s0109_convert_sorted_list_to_binary_search_tree.rs
similarity index 94%
rename from src/n0109_convert_sorted_list_to_binary_search_tree.rs
rename to src/solution/s0109_convert_sorted_list_to_binary_search_tree.rs
index 072c6ea..6bb37b0 100644
--- a/src/n0109_convert_sorted_list_to_binary_search_tree.rs
+++ b/src/solution/s0109_convert_sorted_list_to_binary_search_tree.rs
@@ -21,8 +21,8 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::linked_list::{to_list, ListNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0110_balanced_binary_tree.rs b/src/solution/s0110_balanced_binary_tree.rs
similarity index 93%
rename from src/n0110_balanced_binary_tree.rs
rename to src/solution/s0110_balanced_binary_tree.rs
index 68e1b2a..bb067d0 100644
--- a/src/n0110_balanced_binary_tree.rs
+++ b/src/solution/s0110_balanced_binary_tree.rs
@@ -40,7 +40,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0111_minimum_depth_of_binary_tree.rs b/src/solution/s0111_minimum_depth_of_binary_tree.rs
similarity index 96%
rename from src/n0111_minimum_depth_of_binary_tree.rs
rename to src/solution/s0111_minimum_depth_of_binary_tree.rs
index f537c31..1efb759 100644
--- a/src/n0111_minimum_depth_of_binary_tree.rs
+++ b/src/solution/s0111_minimum_depth_of_binary_tree.rs
@@ -22,7 +22,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0112_path_sum.rs b/src/solution/s0112_path_sum.rs
similarity index 97%
rename from src/n0112_path_sum.rs
rename to src/solution/s0112_path_sum.rs
index 72e34da..2f036b2 100644
--- a/src/n0112_path_sum.rs
+++ b/src/solution/s0112_path_sum.rs
@@ -23,7 +23,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0113_path_sum_ii.rs b/src/solution/s0113_path_sum_ii.rs
similarity index 97%
rename from src/n0113_path_sum_ii.rs
rename to src/solution/s0113_path_sum_ii.rs
index c9914e0..d567e69 100644
--- a/src/n0113_path_sum_ii.rs
+++ b/src/solution/s0113_path_sum_ii.rs
@@ -30,7 +30,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0114_flatten_binary_tree_to_linked_list.rs b/src/solution/s0114_flatten_binary_tree_to_linked_list.rs
similarity index 97%
rename from src/n0114_flatten_binary_tree_to_linked_list.rs
rename to src/solution/s0114_flatten_binary_tree_to_linked_list.rs
index 2b46cd4..9661e9e 100644
--- a/src/n0114_flatten_binary_tree_to_linked_list.rs
+++ b/src/solution/s0114_flatten_binary_tree_to_linked_list.rs
@@ -31,7 +31,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0115_distinct_subsequences.rs b/src/solution/s0115_distinct_subsequences.rs
similarity index 100%
rename from src/n0115_distinct_subsequences.rs
rename to src/solution/s0115_distinct_subsequences.rs
diff --git a/src/n0118_pascals_triangle.rs b/src/solution/s0118_pascals_triangle.rs
similarity index 100%
rename from src/n0118_pascals_triangle.rs
rename to src/solution/s0118_pascals_triangle.rs
diff --git a/src/n0119_pascals_triangle_ii.rs b/src/solution/s0119_pascals_triangle_ii.rs
similarity index 100%
rename from src/n0119_pascals_triangle_ii.rs
rename to src/solution/s0119_pascals_triangle_ii.rs
diff --git a/src/n0120_triangle.rs b/src/solution/s0120_triangle.rs
similarity index 100%
rename from src/n0120_triangle.rs
rename to src/solution/s0120_triangle.rs
diff --git a/src/n0121_best_time_to_buy_and_sell_stock.rs b/src/solution/s0121_best_time_to_buy_and_sell_stock.rs
similarity index 100%
rename from src/n0121_best_time_to_buy_and_sell_stock.rs
rename to src/solution/s0121_best_time_to_buy_and_sell_stock.rs
diff --git a/src/n0122_best_time_to_buy_and_sell_stock_ii.rs b/src/solution/s0122_best_time_to_buy_and_sell_stock_ii.rs
similarity index 100%
rename from src/n0122_best_time_to_buy_and_sell_stock_ii.rs
rename to src/solution/s0122_best_time_to_buy_and_sell_stock_ii.rs
diff --git a/src/n0123_best_time_to_buy_and_sell_stock_iii.rs b/src/solution/s0123_best_time_to_buy_and_sell_stock_iii.rs
similarity index 100%
rename from src/n0123_best_time_to_buy_and_sell_stock_iii.rs
rename to src/solution/s0123_best_time_to_buy_and_sell_stock_iii.rs
diff --git a/src/n0124_binary_tree_maximum_path_sum.rs b/src/solution/s0124_binary_tree_maximum_path_sum.rs
similarity index 98%
rename from src/n0124_binary_tree_maximum_path_sum.rs
rename to src/solution/s0124_binary_tree_maximum_path_sum.rs
index 5517d18..f76f317 100644
--- a/src/n0124_binary_tree_maximum_path_sum.rs
+++ b/src/solution/s0124_binary_tree_maximum_path_sum.rs
@@ -33,7 +33,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0125_valid_palindrome.rs b/src/solution/s0125_valid_palindrome.rs
similarity index 100%
rename from src/n0125_valid_palindrome.rs
rename to src/solution/s0125_valid_palindrome.rs
diff --git a/src/n0126_word_ladder_ii.rs b/src/solution/s0126_word_ladder_ii.rs
similarity index 100%
rename from src/n0126_word_ladder_ii.rs
rename to src/solution/s0126_word_ladder_ii.rs
diff --git a/src/n0127_word_ladder.rs b/src/solution/s0127_word_ladder.rs
similarity index 100%
rename from src/n0127_word_ladder.rs
rename to src/solution/s0127_word_ladder.rs
diff --git a/src/n0128_longest_consecutive_sequence.rs b/src/solution/s0128_longest_consecutive_sequence.rs
similarity index 100%
rename from src/n0128_longest_consecutive_sequence.rs
rename to src/solution/s0128_longest_consecutive_sequence.rs
diff --git a/src/n0129_sum_root_to_leaf_numbers.rs b/src/solution/s0129_sum_root_to_leaf_numbers.rs
similarity index 97%
rename from src/n0129_sum_root_to_leaf_numbers.rs
rename to src/solution/s0129_sum_root_to_leaf_numbers.rs
index 5e423c3..c52dc94 100644
--- a/src/n0129_sum_root_to_leaf_numbers.rs
+++ b/src/solution/s0129_sum_root_to_leaf_numbers.rs
@@ -40,7 +40,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0130_surrounded_regions.rs b/src/solution/s0130_surrounded_regions.rs
similarity index 100%
rename from src/n0130_surrounded_regions.rs
rename to src/solution/s0130_surrounded_regions.rs
diff --git a/src/n0131_palindrome_partitioning.rs b/src/solution/s0131_palindrome_partitioning.rs
similarity index 100%
rename from src/n0131_palindrome_partitioning.rs
rename to src/solution/s0131_palindrome_partitioning.rs
diff --git a/src/n0132_palindrome_partitioning_ii.rs b/src/solution/s0132_palindrome_partitioning_ii.rs
similarity index 100%
rename from src/n0132_palindrome_partitioning_ii.rs
rename to src/solution/s0132_palindrome_partitioning_ii.rs
diff --git a/src/n0134_gas_station.rs b/src/solution/s0134_gas_station.rs
similarity index 100%
rename from src/n0134_gas_station.rs
rename to src/solution/s0134_gas_station.rs
diff --git a/src/n0135_candy.rs b/src/solution/s0135_candy.rs
similarity index 100%
rename from src/n0135_candy.rs
rename to src/solution/s0135_candy.rs
diff --git a/src/n0136_single_number.rs b/src/solution/s0136_single_number.rs
similarity index 100%
rename from src/n0136_single_number.rs
rename to src/solution/s0136_single_number.rs
diff --git a/src/n0137_single_number_ii.rs b/src/solution/s0137_single_number_ii.rs
similarity index 100%
rename from src/n0137_single_number_ii.rs
rename to src/solution/s0137_single_number_ii.rs
diff --git a/src/n0139_word_break.rs b/src/solution/s0139_word_break.rs
similarity index 100%
rename from src/n0139_word_break.rs
rename to src/solution/s0139_word_break.rs
diff --git a/src/n0140_word_break_ii.rs b/src/solution/s0140_word_break_ii.rs
similarity index 100%
rename from src/n0140_word_break_ii.rs
rename to src/solution/s0140_word_break_ii.rs
diff --git a/src/n0143_reorder_list.rs b/src/solution/s0143_reorder_list.rs
similarity index 93%
rename from src/n0143_reorder_list.rs
rename to src/solution/s0143_reorder_list.rs
index 169c44d..06ec32a 100644
--- a/src/n0143_reorder_list.rs
+++ b/src/solution/s0143_reorder_list.rs
@@ -19,7 +19,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0144_binary_tree_preorder_traversal.rs b/src/solution/s0144_binary_tree_preorder_traversal.rs
similarity index 96%
rename from src/n0144_binary_tree_preorder_traversal.rs
rename to src/solution/s0144_binary_tree_preorder_traversal.rs
index 951014c..02ed1f7 100644
--- a/src/n0144_binary_tree_preorder_traversal.rs
+++ b/src/solution/s0144_binary_tree_preorder_traversal.rs
@@ -20,7 +20,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0145_binary_tree_postorder_traversal.rs b/src/solution/s0145_binary_tree_postorder_traversal.rs
similarity index 96%
rename from src/n0145_binary_tree_postorder_traversal.rs
rename to src/solution/s0145_binary_tree_postorder_traversal.rs
index 6649565..2670b5b 100644
--- a/src/n0145_binary_tree_postorder_traversal.rs
+++ b/src/solution/s0145_binary_tree_postorder_traversal.rs
@@ -20,7 +20,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0146_lru_cache.rs b/src/solution/s0146_lru_cache.rs
similarity index 100%
rename from src/n0146_lru_cache.rs
rename to src/solution/s0146_lru_cache.rs
diff --git a/src/n0147_insertion_sort_list.rs b/src/solution/s0147_insertion_sort_list.rs
similarity index 96%
rename from src/n0147_insertion_sort_list.rs
rename to src/solution/s0147_insertion_sort_list.rs
index edcd078..cdcd2d6 100644
--- a/src/n0147_insertion_sort_list.rs
+++ b/src/solution/s0147_insertion_sort_list.rs
@@ -9,7 +9,7 @@
  * <img alt="" src="https://upload.wikimedia.org/wikipedia/commons/0/0f/Insertion-sort-example-300px.gif" style="height:180px; width:300px" /><br />
  * <small>A graphical example of insertion sort. The partial sorted list (black) initially contains only the first element in the list.<br />
  * With each iteration one element (red) is removed from the input data and inserted in-place into the sorted list</small><br />
- *  
+ *
  *
  * <ol>
  * </ol>
@@ -39,7 +39,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0148_sort_list.rs b/src/solution/s0148_sort_list.rs
similarity index 98%
rename from src/n0148_sort_list.rs
rename to src/solution/s0148_sort_list.rs
index 5fd6a8a..4bc8ac1 100644
--- a/src/n0148_sort_list.rs
+++ b/src/solution/s0148_sort_list.rs
@@ -18,7 +18,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0149_max_points_on_a_line.rs b/src/solution/s0149_max_points_on_a_line.rs
similarity index 95%
rename from src/n0149_max_points_on_a_line.rs
rename to src/solution/s0149_max_points_on_a_line.rs
index dff9477..c2faf93 100644
--- a/src/n0149_max_points_on_a_line.rs
+++ b/src/solution/s0149_max_points_on_a_line.rs
@@ -13,7 +13,7 @@
  * |
  * |        o
  * |     o
- * |  o  
+ * |  o
  * +------------->
  * 0  1  2  3  4
  *
@@ -36,7 +36,7 @@
  *
  */
 pub struct Solution {}
-use super::util::point::Point;
+use crate::util::point::Point;
 
 /*
 要回顾下高中数学：已知两点, 求解一般式:
diff --git a/src/n0150_evaluate_reverse_polish_notation.rs b/src/solution/s0150_evaluate_reverse_polish_notation.rs
similarity index 100%
rename from src/n0150_evaluate_reverse_polish_notation.rs
rename to src/solution/s0150_evaluate_reverse_polish_notation.rs
diff --git a/src/n0151_reverse_words_in_a_string.rs b/src/solution/s0151_reverse_words_in_a_string.rs
similarity index 100%
rename from src/n0151_reverse_words_in_a_string.rs
rename to src/solution/s0151_reverse_words_in_a_string.rs
diff --git a/src/n0152_maximum_product_subarray.rs b/src/solution/s0152_maximum_product_subarray.rs
similarity index 100%
rename from src/n0152_maximum_product_subarray.rs
rename to src/solution/s0152_maximum_product_subarray.rs
diff --git a/src/n0153_find_minimum_in_rotated_sorted_array.rs b/src/solution/s0153_find_minimum_in_rotated_sorted_array.rs
similarity index 100%
rename from src/n0153_find_minimum_in_rotated_sorted_array.rs
rename to src/solution/s0153_find_minimum_in_rotated_sorted_array.rs
diff --git a/src/n0154_find_minimum_in_rotated_sorted_array_ii.rs b/src/solution/s0154_find_minimum_in_rotated_sorted_array_ii.rs
similarity index 100%
rename from src/n0154_find_minimum_in_rotated_sorted_array_ii.rs
rename to src/solution/s0154_find_minimum_in_rotated_sorted_array_ii.rs
diff --git a/src/n0155_min_stack.rs b/src/solution/s0155_min_stack.rs
similarity index 100%
rename from src/n0155_min_stack.rs
rename to src/solution/s0155_min_stack.rs
diff --git a/src/n0162_find_peak_element.rs b/src/solution/s0162_find_peak_element.rs
similarity index 100%
rename from src/n0162_find_peak_element.rs
rename to src/solution/s0162_find_peak_element.rs
diff --git a/src/n0164_maximum_gap.rs b/src/solution/s0164_maximum_gap.rs
similarity index 100%
rename from src/n0164_maximum_gap.rs
rename to src/solution/s0164_maximum_gap.rs
diff --git a/src/n0165_compare_version_numbers.rs b/src/solution/s0165_compare_version_numbers.rs
similarity index 100%
rename from src/n0165_compare_version_numbers.rs
rename to src/solution/s0165_compare_version_numbers.rs
diff --git a/src/n0166_fraction_to_recurring_decimal.rs b/src/solution/s0166_fraction_to_recurring_decimal.rs
similarity index 100%
rename from src/n0166_fraction_to_recurring_decimal.rs
rename to src/solution/s0166_fraction_to_recurring_decimal.rs
diff --git a/src/n0167_two_sum_ii_input_array_is_sorted.rs b/src/solution/s0167_two_sum_ii_input_array_is_sorted.rs
similarity index 100%
rename from src/n0167_two_sum_ii_input_array_is_sorted.rs
rename to src/solution/s0167_two_sum_ii_input_array_is_sorted.rs
diff --git a/src/n0168_excel_sheet_column_title.rs b/src/solution/s0168_excel_sheet_column_title.rs
similarity index 100%
rename from src/n0168_excel_sheet_column_title.rs
rename to src/solution/s0168_excel_sheet_column_title.rs
diff --git a/src/n0169_majority_element.rs b/src/solution/s0169_majority_element.rs
similarity index 100%
rename from src/n0169_majority_element.rs
rename to src/solution/s0169_majority_element.rs
diff --git a/src/n0171_excel_sheet_column_number.rs b/src/solution/s0171_excel_sheet_column_number.rs
similarity index 100%
rename from src/n0171_excel_sheet_column_number.rs
rename to src/solution/s0171_excel_sheet_column_number.rs
diff --git a/src/n0172_factorial_trailing_zeroes.rs b/src/solution/s0172_factorial_trailing_zeroes.rs
similarity index 100%
rename from src/n0172_factorial_trailing_zeroes.rs
rename to src/solution/s0172_factorial_trailing_zeroes.rs
diff --git a/src/n0173_binary_search_tree_iterator.rs b/src/solution/s0173_binary_search_tree_iterator.rs
similarity index 94%
rename from src/n0173_binary_search_tree_iterator.rs
rename to src/solution/s0173_binary_search_tree_iterator.rs
index 582e922..caef472 100644
--- a/src/n0173_binary_search_tree_iterator.rs
+++ b/src/solution/s0173_binary_search_tree_iterator.rs
@@ -5,7 +5,7 @@
  *
  * Calling next() will return the next smallest number in the BST.
  *
- *  
+ *
  *
  *
  *
@@ -27,7 +27,7 @@
  * iterator.hasNext(); // return false
  *
  *
- *  
+ *
  *
  * Note:
  *
@@ -38,7 +38,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 use std::cell::RefCell;
 use std::rc::Rc;
 
diff --git a/src/n0174_dungeon_game.rs b/src/solution/s0174_dungeon_game.rs
similarity index 100%
rename from src/n0174_dungeon_game.rs
rename to src/solution/s0174_dungeon_game.rs
diff --git a/src/n0179_largest_number.rs b/src/solution/s0179_largest_number.rs
similarity index 100%
rename from src/n0179_largest_number.rs
rename to src/solution/s0179_largest_number.rs
diff --git a/src/n0187_repeated_dna_sequences.rs b/src/solution/s0187_repeated_dna_sequences.rs
similarity index 100%
rename from src/n0187_repeated_dna_sequences.rs
rename to src/solution/s0187_repeated_dna_sequences.rs
diff --git a/src/n0188_best_time_to_buy_and_sell_stock_iv.rs b/src/solution/s0188_best_time_to_buy_and_sell_stock_iv.rs
similarity index 100%
rename from src/n0188_best_time_to_buy_and_sell_stock_iv.rs
rename to src/solution/s0188_best_time_to_buy_and_sell_stock_iv.rs
diff --git a/src/n0189_rotate_array.rs b/src/solution/s0189_rotate_array.rs
similarity index 100%
rename from src/n0189_rotate_array.rs
rename to src/solution/s0189_rotate_array.rs
diff --git a/src/n0198_house_robber.rs b/src/solution/s0198_house_robber.rs
similarity index 100%
rename from src/n0198_house_robber.rs
rename to src/solution/s0198_house_robber.rs
diff --git a/src/n0199_binary_tree_right_side_view.rs b/src/solution/s0199_binary_tree_right_side_view.rs
similarity index 97%
rename from src/n0199_binary_tree_right_side_view.rs
rename to src/solution/s0199_binary_tree_right_side_view.rs
index 403a340..c580970 100644
--- a/src/n0199_binary_tree_right_side_view.rs
+++ b/src/solution/s0199_binary_tree_right_side_view.rs
@@ -18,7 +18,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0200_number_of_islands.rs b/src/solution/s0200_number_of_islands.rs
similarity index 100%
rename from src/n0200_number_of_islands.rs
rename to src/solution/s0200_number_of_islands.rs
diff --git a/src/n0201_bitwise_and_of_numbers_range.rs b/src/solution/s0201_bitwise_and_of_numbers_range.rs
similarity index 100%
rename from src/n0201_bitwise_and_of_numbers_range.rs
rename to src/solution/s0201_bitwise_and_of_numbers_range.rs
diff --git a/src/n0202_happy_number.rs b/src/solution/s0202_happy_number.rs
similarity index 100%
rename from src/n0202_happy_number.rs
rename to src/solution/s0202_happy_number.rs
diff --git a/src/n0203_remove_linked_list_elements.rs b/src/solution/s0203_remove_linked_list_elements.rs
similarity index 95%
rename from src/n0203_remove_linked_list_elements.rs
rename to src/solution/s0203_remove_linked_list_elements.rs
index 290923d..f8d9bc4 100644
--- a/src/n0203_remove_linked_list_elements.rs
+++ b/src/solution/s0203_remove_linked_list_elements.rs
@@ -12,7 +12,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0204_count_primes.rs b/src/solution/s0204_count_primes.rs
similarity index 100%
rename from src/n0204_count_primes.rs
rename to src/solution/s0204_count_primes.rs
diff --git a/src/n0205_isomorphic_strings.rs b/src/solution/s0205_isomorphic_strings.rs
similarity index 100%
rename from src/n0205_isomorphic_strings.rs
rename to src/solution/s0205_isomorphic_strings.rs
diff --git a/src/n0206_reverse_linked_list.rs b/src/solution/s0206_reverse_linked_list.rs
similarity index 94%
rename from src/n0206_reverse_linked_list.rs
rename to src/solution/s0206_reverse_linked_list.rs
index bdbe34e..4689f41 100644
--- a/src/n0206_reverse_linked_list.rs
+++ b/src/solution/s0206_reverse_linked_list.rs
@@ -16,7 +16,7 @@
  *
  */
 pub struct Solution {}
-use super::util::linked_list::{to_list, ListNode};
+use crate::util::linked_list::{to_list, ListNode};
 
 // submission codes start here
 
diff --git a/src/n0207_course_schedule.rs b/src/solution/s0207_course_schedule.rs
similarity index 100%
rename from src/n0207_course_schedule.rs
rename to src/solution/s0207_course_schedule.rs
diff --git a/src/n0208_implement_trie_prefix_tree.rs b/src/solution/s0208_implement_trie_prefix_tree.rs
similarity index 100%
rename from src/n0208_implement_trie_prefix_tree.rs
rename to src/solution/s0208_implement_trie_prefix_tree.rs
diff --git a/src/n0209_minimum_size_subarray_sum.rs b/src/solution/s0209_minimum_size_subarray_sum.rs
similarity index 100%
rename from src/n0209_minimum_size_subarray_sum.rs
rename to src/solution/s0209_minimum_size_subarray_sum.rs
diff --git a/src/n0210_course_schedule_ii.rs b/src/solution/s0210_course_schedule_ii.rs
similarity index 100%
rename from src/n0210_course_schedule_ii.rs
rename to src/solution/s0210_course_schedule_ii.rs
diff --git a/src/n0211_add_and_search_word_data_structure_design.rs b/src/solution/s0211_add_and_search_word_data_structure_design.rs
similarity index 100%
rename from src/n0211_add_and_search_word_data_structure_design.rs
rename to src/solution/s0211_add_and_search_word_data_structure_design.rs
diff --git a/src/n0212_word_search_ii.rs b/src/solution/s0212_word_search_ii.rs
similarity index 100%
rename from src/n0212_word_search_ii.rs
rename to src/solution/s0212_word_search_ii.rs
diff --git a/src/n0213_house_robber_ii.rs b/src/solution/s0213_house_robber_ii.rs
similarity index 100%
rename from src/n0213_house_robber_ii.rs
rename to src/solution/s0213_house_robber_ii.rs
diff --git a/src/n0214_shortest_palindrome.rs b/src/solution/s0214_shortest_palindrome.rs
similarity index 100%
rename from src/n0214_shortest_palindrome.rs
rename to src/solution/s0214_shortest_palindrome.rs
diff --git a/src/n0215_kth_largest_element_in_an_array.rs b/src/solution/s0215_kth_largest_element_in_an_array.rs
similarity index 100%
rename from src/n0215_kth_largest_element_in_an_array.rs
rename to src/solution/s0215_kth_largest_element_in_an_array.rs
diff --git a/src/n0216_combination_sum_iii.rs b/src/solution/s0216_combination_sum_iii.rs
similarity index 100%
rename from src/n0216_combination_sum_iii.rs
rename to src/solution/s0216_combination_sum_iii.rs
diff --git a/src/n0217_contains_duplicate.rs b/src/solution/s0217_contains_duplicate.rs
similarity index 100%
rename from src/n0217_contains_duplicate.rs
rename to src/solution/s0217_contains_duplicate.rs
diff --git a/src/n0218_the_skyline_problem.rs b/src/solution/s0218_the_skyline_problem.rs
similarity index 100%
rename from src/n0218_the_skyline_problem.rs
rename to src/solution/s0218_the_skyline_problem.rs
diff --git a/src/n0219_contains_duplicate_ii.rs b/src/solution/s0219_contains_duplicate_ii.rs
similarity index 100%
rename from src/n0219_contains_duplicate_ii.rs
rename to src/solution/s0219_contains_duplicate_ii.rs
diff --git a/src/n0220_contains_duplicate_iii.rs b/src/solution/s0220_contains_duplicate_iii.rs
similarity index 100%
rename from src/n0220_contains_duplicate_iii.rs
rename to src/solution/s0220_contains_duplicate_iii.rs
diff --git a/src/n0221_maximal_square.rs b/src/solution/s0221_maximal_square.rs
similarity index 100%
rename from src/n0221_maximal_square.rs
rename to src/solution/s0221_maximal_square.rs
diff --git a/src/n0222_count_complete_tree_nodes.rs b/src/solution/s0222_count_complete_tree_nodes.rs
similarity index 98%
rename from src/n0222_count_complete_tree_nodes.rs
rename to src/solution/s0222_count_complete_tree_nodes.rs
index c511399..189fb3d 100644
--- a/src/n0222_count_complete_tree_nodes.rs
+++ b/src/solution/s0222_count_complete_tree_nodes.rs
@@ -22,7 +22,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0223_rectangle_area.rs b/src/solution/s0223_rectangle_area.rs
similarity index 100%
rename from src/n0223_rectangle_area.rs
rename to src/solution/s0223_rectangle_area.rs
diff --git a/src/n0224_basic_calculator.rs b/src/solution/s0224_basic_calculator.rs
similarity index 100%
rename from src/n0224_basic_calculator.rs
rename to src/solution/s0224_basic_calculator.rs
diff --git a/src/n0225_implement_stack_using_queues.rs b/src/solution/s0225_implement_stack_using_queues.rs
similarity index 100%
rename from src/n0225_implement_stack_using_queues.rs
rename to src/solution/s0225_implement_stack_using_queues.rs
diff --git a/src/n0226_invert_binary_tree.rs b/src/solution/s0226_invert_binary_tree.rs
similarity index 97%
rename from src/n0226_invert_binary_tree.rs
rename to src/solution/s0226_invert_binary_tree.rs
index 29e2a95..30bd001 100644
--- a/src/n0226_invert_binary_tree.rs
+++ b/src/solution/s0226_invert_binary_tree.rs
@@ -30,7 +30,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0227_basic_calculator_ii.rs b/src/solution/s0227_basic_calculator_ii.rs
similarity index 100%
rename from src/n0227_basic_calculator_ii.rs
rename to src/solution/s0227_basic_calculator_ii.rs
diff --git a/src/n0228_summary_ranges.rs b/src/solution/s0228_summary_ranges.rs
similarity index 100%
rename from src/n0228_summary_ranges.rs
rename to src/solution/s0228_summary_ranges.rs
diff --git a/src/n0229_majority_element_ii.rs b/src/solution/s0229_majority_element_ii.rs
similarity index 100%
rename from src/n0229_majority_element_ii.rs
rename to src/solution/s0229_majority_element_ii.rs
diff --git a/src/n0230_kth_smallest_element_in_a_bst.rs b/src/solution/s0230_kth_smallest_element_in_a_bst.rs
similarity index 97%
rename from src/n0230_kth_smallest_element_in_a_bst.rs
rename to src/solution/s0230_kth_smallest_element_in_a_bst.rs
index 65de448..fe14721 100644
--- a/src/n0230_kth_smallest_element_in_a_bst.rs
+++ b/src/solution/s0230_kth_smallest_element_in_a_bst.rs
@@ -36,7 +36,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0231_power_of_two.rs b/src/solution/s0231_power_of_two.rs
similarity index 100%
rename from src/n0231_power_of_two.rs
rename to src/solution/s0231_power_of_two.rs
diff --git a/src/n0232_implement_queue_using_stacks.rs b/src/solution/s0232_implement_queue_using_stacks.rs
similarity index 100%
rename from src/n0232_implement_queue_using_stacks.rs
rename to src/solution/s0232_implement_queue_using_stacks.rs
diff --git a/src/n0233_number_of_digit_one.rs b/src/solution/s0233_number_of_digit_one.rs
similarity index 100%
rename from src/n0233_number_of_digit_one.rs
rename to src/solution/s0233_number_of_digit_one.rs
diff --git a/src/n0238_product_of_array_except_self.rs b/src/solution/s0238_product_of_array_except_self.rs
similarity index 100%
rename from src/n0238_product_of_array_except_self.rs
rename to src/solution/s0238_product_of_array_except_self.rs
diff --git a/src/n0239_sliding_window_maximum.rs b/src/solution/s0239_sliding_window_maximum.rs
similarity index 100%
rename from src/n0239_sliding_window_maximum.rs
rename to src/solution/s0239_sliding_window_maximum.rs
diff --git a/src/n0241_different_ways_to_add_parentheses.rs b/src/solution/s0241_different_ways_to_add_parentheses.rs
similarity index 100%
rename from src/n0241_different_ways_to_add_parentheses.rs
rename to src/solution/s0241_different_ways_to_add_parentheses.rs
diff --git a/src/n0242_valid_anagram.rs b/src/solution/s0242_valid_anagram.rs
similarity index 100%
rename from src/n0242_valid_anagram.rs
rename to src/solution/s0242_valid_anagram.rs
diff --git a/src/n0257_binary_tree_paths.rs b/src/solution/s0257_binary_tree_paths.rs
similarity index 97%
rename from src/n0257_binary_tree_paths.rs
rename to src/solution/s0257_binary_tree_paths.rs
index ef5254c..c5d6d33 100644
--- a/src/n0257_binary_tree_paths.rs
+++ b/src/solution/s0257_binary_tree_paths.rs
@@ -22,7 +22,7 @@
  *
  */
 pub struct Solution {}
-use super::util::tree::{to_tree, TreeNode};
+use crate::util::tree::{to_tree, TreeNode};
 
 // submission codes start here
 
diff --git a/src/n0258_add_digits.rs b/src/solution/s0258_add_digits.rs
similarity index 100%
rename from src/n0258_add_digits.rs
rename to src/solution/s0258_add_digits.rs
diff --git a/src/n0260_single_number_iii.rs b/src/solution/s0260_single_number_iii.rs
similarity index 100%
rename from src/n0260_single_number_iii.rs
rename to src/solution/s0260_single_number_iii.rs
diff --git a/src/n0263_ugly_number.rs b/src/solution/s0263_ugly_number.rs
similarity index 100%
rename from src/n0263_ugly_number.rs
rename to src/solution/s0263_ugly_number.rs
diff --git a/src/n0264_ugly_number_ii.rs b/src/solution/s0264_ugly_number_ii.rs
similarity index 100%
rename from src/n0264_ugly_number_ii.rs
rename to src/solution/s0264_ugly_number_ii.rs
diff --git a/src/n0268_missing_number.rs b/src/solution/s0268_missing_number.rs
similarity index 100%
rename from src/n0268_missing_number.rs
rename to src/solution/s0268_missing_number.rs
diff --git a/src/n0273_integer_to_english_words.rs b/src/solution/s0273_integer_to_english_words.rs
similarity index 100%
rename from src/n0273_integer_to_english_words.rs
rename to src/solution/s0273_integer_to_english_words.rs
diff --git a/src/n0274_h_index.rs b/src/solution/s0274_h_index.rs
similarity index 100%
rename from src/n0274_h_index.rs
rename to src/solution/s0274_h_index.rs
diff --git a/src/n0275_h_index_ii.rs b/src/solution/s0275_h_index_ii.rs
similarity index 100%
rename from src/n0275_h_index_ii.rs
rename to src/solution/s0275_h_index_ii.rs
diff --git a/src/n0279_perfect_squares.rs b/src/solution/s0279_perfect_squares.rs
similarity index 100%
rename from src/n0279_perfect_squares.rs
rename to src/solution/s0279_perfect_squares.rs
diff --git a/src/n0282_expression_add_operators.rs b/src/solution/s0282_expression_add_operators.rs
similarity index 100%
rename from src/n0282_expression_add_operators.rs
rename to src/solution/s0282_expression_add_operators.rs
diff --git a/src/n0283_move_zeroes.rs b/src/solution/s0283_move_zeroes.rs
similarity index 100%
rename from src/n0283_move_zeroes.rs
rename to src/solution/s0283_move_zeroes.rs
diff --git a/src/n0287_find_the_duplicate_number.rs b/src/solution/s0287_find_the_duplicate_number.rs
similarity index 100%
rename from src/n0287_find_the_duplicate_number.rs
rename to src/solution/s0287_find_the_duplicate_number.rs
diff --git a/src/n0289_game_of_life.rs b/src/solution/s0289_game_of_life.rs
similarity index 100%
rename from src/n0289_game_of_life.rs
rename to src/solution/s0289_game_of_life.rs
diff --git a/src/n0290_word_pattern.rs b/src/solution/s0290_word_pattern.rs
similarity index 100%
rename from src/n0290_word_pattern.rs
rename to src/solution/s0290_word_pattern.rs
diff --git a/src/n0292_nim_game.rs b/src/solution/s0292_nim_game.rs
similarity index 100%
rename from src/n0292_nim_game.rs
rename to src/solution/s0292_nim_game.rs
diff --git a/src/n0295_find_median_from_data_stream.rs b/src/solution/s0295_find_median_from_data_stream.rs
similarity index 100%
rename from src/n0295_find_median_from_data_stream.rs
rename to src/solution/s0295_find_median_from_data_stream.rs
diff --git a/src/n0299_bulls_and_cows.rs b/src/solution/s0299_bulls_and_cows.rs
similarity index 100%
rename from src/n0299_bulls_and_cows.rs
rename to src/solution/s0299_bulls_and_cows.rs
diff --git a/src/n0300_longest_increasing_subsequence.rs b/src/solution/s0300_longest_increasing_subsequence.rs
similarity index 100%
rename from src/n0300_longest_increasing_subsequence.rs
rename to src/solution/s0300_longest_increasing_subsequence.rs
diff --git a/src/n0301_remove_invalid_parentheses.rs b/src/solution/s0301_remove_invalid_parentheses.rs
similarity index 100%
rename from src/n0301_remove_invalid_parentheses.rs
rename to src/solution/s0301_remove_invalid_parentheses.rs
diff --git a/src/n0303_range_sum_query_immutable.rs b/src/solution/s0303_range_sum_query_immutable.rs
similarity index 100%
rename from src/n0303_range_sum_query_immutable.rs
rename to src/solution/s0303_range_sum_query_immutable.rs
diff --git a/src/n0304_range_sum_query_2d_immutable.rs b/src/solution/s0304_range_sum_query_2d_immutable.rs
similarity index 100%
rename from src/n0304_range_sum_query_2d_immutable.rs
rename to src/solution/s0304_range_sum_query_2d_immutable.rs
diff --git a/src/n0306_additive_number.rs b/src/solution/s0306_additive_number.rs
similarity index 100%
rename from src/n0306_additive_number.rs
rename to src/solution/s0306_additive_number.rs
diff --git a/src/n0307_range_sum_query_mutable.rs b/src/solution/s0307_range_sum_query_mutable.rs
similarity index 100%
rename from src/n0307_range_sum_query_mutable.rs
rename to src/solution/s0307_range_sum_query_mutable.rs
diff --git a/src/n0309_best_time_to_buy_and_sell_stock_with_cooldown.rs b/src/solution/s0309_best_time_to_buy_and_sell_stock_with_cooldown.rs
similarity index 100%
rename from src/n0309_best_time_to_buy_and_sell_stock_with_cooldown.rs
rename to src/solution/s0309_best_time_to_buy_and_sell_stock_with_cooldown.rs
diff --git a/src/n0310_minimum_height_trees.rs b/src/solution/s0310_minimum_height_trees.rs
similarity index 100%
rename from src/n0310_minimum_height_trees.rs
rename to src/solution/s0310_minimum_height_trees.rs
diff --git a/src/n0312_burst_balloons.rs b/src/solution/s0312_burst_balloons.rs
similarity index 100%
rename from src/n0312_burst_balloons.rs
rename to src/solution/s0312_burst_balloons.rs
diff --git a/src/n0313_super_ugly_number.rs b/src/solution/s0313_super_ugly_number.rs
similarity index 100%
rename from src/n0313_super_ugly_number.rs
rename to src/solution/s0313_super_ugly_number.rs
diff --git a/src/n0509_fibonacci_number.rs b/src/solution/s0509_fibonacci_number.rs
similarity index 100%
rename from src/n0509_fibonacci_number.rs
rename to src/solution/s0509_fibonacci_number.rs
diff --git a/src/n0704_binary_search.rs b/src/solution/s0704_binary_search.rs
similarity index 100%
rename from src/n0704_binary_search.rs
rename to src/solution/s0704_binary_search.rs
diff --git a/src/n0969_pancake_sorting.rs b/src/solution/s0969_pancake_sorting.rs
similarity index 100%
rename from src/n0969_pancake_sorting.rs
rename to src/solution/s0969_pancake_sorting.rs
diff --git a/src/n1018_binary_prefix_divisible_by_5.rs b/src/solution/s1018_binary_prefix_divisible_by_5.rs
similarity index 100%
rename from src/n1018_binary_prefix_divisible_by_5.rs
rename to src/solution/s1018_binary_prefix_divisible_by_5.rs
diff --git a/src/n1046_last_stone_weight.rs b/src/solution/s1046_last_stone_weight.rs
similarity index 100%
rename from src/n1046_last_stone_weight.rs
rename to src/solution/s1046_last_stone_weight.rs