LeetCode OJ：Implement Trie (Prefix Tree)（实现一个字典树(前缀树)）

Implement a trie with insert, search, and startsWith methods.

实现字典树，前面好像有道题做过类似的东西，代码如下：

 class TrieNode {
 public:
     // Initialize your data structure here.
     TrieNode():isLeaf(false)
     {
         for(auto & t : dic){
             t = NULL;
         }
     }
     TrieNode * dic[];
     bool isLeaf;
 };

 class Trie {
 public:
     Trie() {
         root = new TrieNode();
     }

     // Inserts a word into the trie.
     void insert(string word) {
         TrieNode * p = root;
         for(int i = ; i < word.size(); ++i){
             int index = word[i] - 'a';
             if(p->dic[index] == NULL)
                 p->dic[index] = new TrieNode();
             p = p->dic[index];
         }
         p->isLeaf = true;
     }

     // Returns if the word is in the trie.
     bool search(string word) {
         TrieNode * p = root;
         for(int i = ; i < word.size(); ++i){
             int index = word[i] - 'a';
             if(p->dic[index] == NULL)
                 return false;
             p = p->dic[index];
         }
         return p->isLeaf;
     }

     // Returns if there is any word in the trie
     // that starts with the given prefix.
     bool startsWith(string prefix) {
         TrieNode * p = root;
         for(int i = ; i < prefix.size(); ++i){
             int index = prefix[i] - 'a';
             if(p->dic[index] == NULL)
                 return false;
             p = p->dic[index];
         }
         return true;
     }

 private:
     TrieNode* root;
 };

 // Your Trie object will be instantiated and called as such:
 // Trie trie;
 // trie.insert("somestring");
 // trie.search("key");