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 = ;
         ends = ;
     }

     /** Inserts a word into the trie. */
     void insert(string word) {
         Trie* p = this;
         for(int i = ; 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 = ; i < word.size(); ++i) {
             if(p->nxt.find(word[i]) == p->nxt.end()) return false;
             p = p->nxt[word[i]];
         }
         return p->ends != ;
     }

     /** 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 = ; 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);
  */