LeetCode 208 Implement Trie (Prefix Tree) 字典树（前缀树）

Implement a trie with insert, search, and startsWith methods.
Note:
You may assume that all inputs are consist of lowercase letters a-z.

 class TrieNode{
 public:
     TrieNode():isWord(false)
     {
         memset(next,,sizeof(TrieNode*)*);
     }
     TrieNode(char _c):c(_c),isWord(false)
     {
         memset(next,,sizeof(TreeNode*)*);
     }
     TrieNode* next[];
     char c;
     bool isWord;
 };

 class Trie {
 public:
     /** Initialize your data structure here. */
     Trie() {
         root=new TrieNode();
     }

     /** Inserts a word into the trie. */
     void insert(string word) {
         TrieNode* p=root;
         int id;
         for(char c:word)
         {
             id=c-'a';
             if(p->next[id]==nullptr)
                 p->next[id]=new TrieNode(c);
             p=p->next[id];
         }
         p->isWord=true;
     }

     /** Returns if the word is in the trie. */
     bool search(string word) {
         TrieNode* p=root;
         int id;
         for(char c:word)
         {
             id=c-'a';
             if(p->next[id]==nullptr)
                 return false;
             p=p->next[id];
         }
         return p->isWord;
     }

     /** Returns if there is any word in the trie that starts with the given prefix. */
     bool startsWith(string prefix) {
         TrieNode* p=root;
         int id;
         for(char c:prefix)
         {
             id=c-'a';
             if(p->next[id]==nullptr)
                 return false;
             p=p->next[id];
         }
         return true;
     }
 private:
     TrieNode* root;
 };

 /**
  * 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);
  */