leetcode-add-and-search-word

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题目大意

　　https://leetcode.com/problems/add-and-search-word-data-structure-design/

　　实现高效的方法，能够支持频繁插入和搜索字符串，注意搜索字符串可能有.进行模糊匹配

题目分析

　　很明显利用trie树（trie树的实现那道题看之前的博客），只不过本题搜索可能含有.那就利用递归即可。

代码

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class TrieNode {
    public char ch;
    public int freq;
    public TrieNode[] child;
    
    public TrieNode() {
        child = new TrieNode[26];
    }
}
class Trie {
    public TrieNode root; 
    /** Initialize your data structure here. */
    public Trie() {
        root = new TrieNode();
    }
    
    /** Inserts a word into the trie. */
    public void insert(String word) {
        char[] w = word.toCharArray();
        int len = w.length;
        TrieNode cur = root;
        for (int i = 0; i < len; i++) {
            if (cur.child[w[i] - 'a'] == null) {
                cur.child[w[i] - 'a'] = new TrieNode();
                cur = cur.child[w[i] - 'a'];
                cur.ch = w[i];
            } else {
                cur = cur.child[w[i] - 'a'];
            }
            if (i == len - 1) {
                cur.freq++;
            }
        }
    }
    
    public boolean searchReg(String word, int idx, TrieNode r) {
        if (idx > word.length() - 1) {
            if (r.freq > 0) {
                return true;
            }
            return false;
        }
        if (r == null || r.child == null) {
            return false;
        }
        char w = word.charAt(idx);
        if (w != '.') {
            if (r.child[w - 'a'] != null) {
                return searchReg(word, idx + 1, r.child[w - 'a']);
            }
        } else {
            for (int i = 0; i < 26; i++) {
                if (r.child[i] != null && searchReg(word, idx + 1, r.child[i])) {
                    return true;
                }
            }
        }
        return false;
    }
    
}
public class WordDictionary {
    private Trie trie;
    /** Initialize your data structure here. */
    public WordDictionary() {
        trie = new Trie();
    }
    
    /** Adds a word into the data structure. */
    public void addWord(String word) {
        trie.insert(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 trie.searchReg(word, 0, trie.root);
    }
}
/**
 * Your WordDictionary object will be instantiated and called as such:
 * WordDictionary obj = new WordDictionary();
 * obj.addWord(word);
 * boolean param_2 = obj.search(word);
 */