LeetCode 实现 Trie (前缀树)

题目链接：https://leetcode-cn.com/problems/implement-trie-prefix-tree/

题目大意：

　　略。

分析：

　　字典树模板.

代码如下：

class Trie {
public:
    int passed; // 记录经过这个节点的字符串数量
    int ends;   // 记录有多少个字符串以这个节点结尾
    unordered_map< char, Trie* > nxt;
    
    /** Initialize your data structure here. */
    Trie() {
        passed = 0;
        ends = 0;
    }
    
    /** Inserts a word into the trie. */
    void insert(string word) {
        Trie* p = this;
        for(int i = 0; i < word.size(); ++i) {
            if(p->nxt.find(word[i]) == p->nxt.end()) {
                p->nxt[word[i]] = new Trie();
            }
            ++p->passed;
            p = p->nxt[word[i]];
        }
        ++p->ends;
    }
    
    /** Returns if the word is in the trie. */
    bool search(string word) {
        Trie* p = this;
        for(int i = 0; i < word.size(); ++i) {
            if(p->nxt.find(word[i]) == p->nxt.end()) return false;
            p = p->nxt[word[i]];
        }
        return p->ends != 0;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    bool startsWith(string prefix) {
        Trie* p = this;
        for(int i = 0; i < prefix.size(); ++i) {
            if(p->nxt.find(prefix[i]) == p->nxt.end()) return false;
            p = p->nxt[prefix[i]];
        }
        return true;
    }
};

/**
 * Your Trie object will be instantiated and called as such:
 * Trie* obj = new Trie();
 * obj->insert(word);
 * bool param_2 = obj->search(word);
 * bool param_3 = obj->startsWith(prefix);
 */