LeetCode Add and Search Word - Data structure design Trie

最新推荐文章于 2019-08-05 10:40:12 发布

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本文介绍了一种使用Trie树（字典树）的数据结构来实现单词字典的方法，该字典支持添加单词及搜索包含通配符'.'的单词。通过递归深度优先搜索实现了对带有通配符的字符串进行高效匹配。

思路：

根据hint应该用trie树，否则肯定超时。

java code：

public class WordDictionary {
    class TrieNode {
        boolean isLeaf;
        TrieNode[] children = new TrieNode[26];

        public TrieNode() {
        }
    }
    private TrieNode 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.isLeaf = true;
    }

    // Returns if the word is in the data structure. A word could
    // contain the dot character '.' to represent any one letter.
    private boolean dfs(String word, TrieNode cur) {
        if(cur == null) return false;
        if(word.length() == 0) return cur.isLeaf;
        TrieNode[] children = cur.children;
        char c = word.charAt(0);
        if(c == '.') {
            for(TrieNode child : children) {
                if(child != null && dfs(word.substring(1), child)) {
                    return true;
                }
            }
            return false;
        }else if(children[c - 'a'] != null) {
            return dfs(word.substring(1), children[c - 'a']);
        }else {
            return false;
        }
    }
    public boolean search(String word) {
        return dfs(word, root);
    }    
}