README_EN.md

211. Design Add and Search Words Data Structure

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Description

Design a data structure that supports adding new words and finding if a string matches any previously added string.

Implement the WordDictionary class:

• WordDictionary() Initializes the object.
• void addWord(word) Adds word to the data structure, it can be matched later.
• bool search(word) Returns true if there is any string in the data structure that matches word or false otherwise. word may contain dots '.' where dots can be matched with any letter.

 

Example:

Input
["WordDictionary","addWord","addWord","addWord","search","search","search","search"]
[[],["bad"],["dad"],["mad"],["pad"],["bad"],[".ad"],["b.."]]
Output
[null,null,null,null,false,true,true,true]

Explanation
WordDictionary wordDictionary = new WordDictionary();
wordDictionary.addWord("bad");
wordDictionary.addWord("dad");
wordDictionary.addWord("mad");
wordDictionary.search("pad"); // return False
wordDictionary.search("bad"); // return True
wordDictionary.search(".ad"); // return True
wordDictionary.search("b.."); // return True

 

Constraints:

• 1 <= word.length <= 500
• word in addWord consists lower-case English letters.
• word in search consist of  '.' or lower-case English letters.
• At most 50000 calls will be made to addWord and search.

Solutions

Python3

class Trie:

    def __init__(self):
        self.children = [None] * 26
        self.is_end = False


class WordDictionary:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.trie = Trie()

    def addWord(self, word: str) -> None:
        node = self.trie
        for c in word:
            index = ord(c) - ord('a')
            if node.children[index] is None:
                node.children[index] = Trie()
            node = node.children[index]
        node.is_end = True

    def search(self, word: str) -> bool:
        return self._search(word, self.trie)

    def _search(self, word: str, node: Trie) -> bool:
        for i in range(len(word)):
            c = word[i]
            index = ord(c) - ord('a')
            if c != '.' and node.children[index] is None:
                return False
            if c == '.':
                for j in range(26):
                    if node.children[j] is not None and self._search(word[i + 1:], node.children[j]):
                        return True
                return False
            node = node.children[index]
        return node.is_end

# Your WordDictionary object will be instantiated and called as such:
# obj = WordDictionary()
# obj.addWord(word)
# param_2 = obj.search(word)

Java

class WordDictionary {
    class Trie {
        Trie[] children;
        boolean isEnd;
        Trie() {
            children = new Trie[26];
            isEnd = false;
        }
    }

    private Trie trie;

    /** Initialize your data structure here. */
    public WordDictionary() {
        trie = new Trie();
    }

    public void addWord(String word) {
        Trie node = trie;
        for (int i = 0; i < word.length(); ++i) {
            char c = word.charAt(i);
            int index = c - 'a';
            if (node.children[index] == null) {
                node.children[index] = new Trie();
            }
            node = node.children[index];
        }
        node.isEnd = true;
    }

    public boolean search(String word) {
        return search(word, trie);
    }

    private boolean search(String word, Trie node) {
        for (int i = 0; i < word.length(); ++i) {
            char c = word.charAt(i);
            int index = c - 'a';
            if (c != '.' && node.children[index] == null) {
                return false;
            }
            if (c == '.') {
                for (int j = 0; j < 26; ++j) {
                    if (node.children[j] != null && search(word.substring(i + 1), node.children[j])) {
                        return true;
                    }
                }
                return false;
            }
            node = node.children[index];
        }
        return node.isEnd;
    }
}

/**
 * Your WordDictionary object will be instantiated and called as such:
 * WordDictionary obj = new WordDictionary();
 * obj.addWord(word);
 * boolean param_2 = obj.search(word);
 */

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