D-5.md

🔮 Question

Design a data structure that supports the following two operations: void addWord(word) bool search(word) search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.
Example:
addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true
Note:
You may assume that all words are consist of lowercase letters a-z.

🐉 Solution

class WordDictionary {

    private TrieNode root; 

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

    /** Adds a word into the data structure. */
    public void addWord(String word) {
        TrieNode node = root;
        for (char c: word.toCharArray()){
            if(node.children[c - 'a'] == null){
                node.children[c - 'a'] = new TrieNode();
            }
            node = node.children[c - 'a'];
        }
        node.val = word;
    }

    /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */
    public boolean search(String word) {
        return match(word, 0, root);
    }

    private boolean match(String word, int depth, TrieNode node){
        if(depth == word.length()) return !node.val.equals("");
        if(word.charAt(depth) != '.'){
            return (node.children[word.charAt(depth) - 'a'] != null && match(word, depth + 1, node.children[word.charAt(depth) - 'a'] ));
        }
        else{
            for (int i = 0; i < node.children.length; i++){
                if(node.children[i] != null && match(word, depth + 1, node.children[i]))
                    return true;
            }
        }
        return false;
    }
}
class TrieNode{
        public TrieNode [] children = new TrieNode[26];
        public String val = "";
    }
/**
 * Your WordDictionary object will be instantiated and called as such:
 * WordDictionary obj = new WordDictionary();
 * obj.addWord(word);
 * boolean param_2 = obj.search(word);
 */