You are given two integers m
and n
representing a 0-indexed m x n
grid. You are also given two 2D integer arrays guards
and walls
where guards[i] = [rowi, coli]
and walls[j] = [rowj, colj]
represent the positions of the ith
guard and jth
wall respectively.
A guard can see every cell in the four cardinal directions (north, east, south, or west) starting from their position unless obstructed by a wall or another guard. A cell is guarded if there is at least one guard that can see it.
Return the number of unoccupied cells that are not guarded.
Input: m = 4, n = 6, guards = [[0,0],[1,1],[2,3]], walls = [[0,1],[2,2],[1,4]] Output: 7 Explanation: The guarded and unguarded cells are shown in red and green respectively in the above diagram. There are a total of 7 unguarded cells, so we return 7.
Input: m = 3, n = 3, guards = [[1,1]], walls = [[0,1],[1,0],[2,1],[1,2]] Output: 4 Explanation: The unguarded cells are shown in green in the above diagram. There are a total of 4 unguarded cells, so we return 4.
1 <= m, n <= 105
2 <= m * n <= 105
1 <= guards.length, walls.length <= 5 * 104
2 <= guards.length + walls.length <= m * n
guards[i].length == walls[j].length == 2
0 <= rowi, rowj < m
0 <= coli, colj < n
- All the positions in
guards
andwalls
are unique.
impl Solution {
pub fn count_unguarded(m: i32, n: i32, guards: Vec<Vec<i32>>, walls: Vec<Vec<i32>>) -> i32 {
let (m, n) = (m as usize, n as usize);
let mut grid = vec![vec![0; n]; m];
let mut ret = 0;
for i in 0..guards.len() {
grid[guards[i][0] as usize][guards[i][1] as usize] = 1;
}
for i in 0..walls.len() {
grid[walls[i][0] as usize][walls[i][1] as usize] = 2;
}
for r in 0..m {
let mut can_see = false;
for c in 0..n {
match grid[r][c] {
1 => can_see = true,
2 => can_see = false,
_ if can_see => grid[r][c] = 3,
_ => (),
}
}
can_see = false;
for c in (0..n).rev() {
match grid[r][c] {
1 => can_see = true,
2 => can_see = false,
_ if can_see => grid[r][c] = 3,
_ => (),
}
}
}
for c in 0..n {
let mut can_see = false;
for r in 0..m {
match grid[r][c] {
1 => can_see = true,
2 => can_see = false,
_ if can_see => grid[r][c] = 3,
_ => (),
}
}
can_see = false;
for r in (0..m).rev() {
match grid[r][c] {
1 => can_see = true,
2 => can_see = false,
_ if can_see => grid[r][c] = 3,
_ => (),
}
if grid[r][c] == 0 {
ret += 1;
}
}
}
ret
}
}