Implement Trie (Prefix Tree) - LeetCode

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

Note:
You may assume that all inputs are consist of lowercase letters a-z.

思路：应该就是字典树。

 class TrieNode {
 public:
     TrieNode *dic[];
     // Initialize your data structure here.
     TrieNode() {
         for (int i = ; i < ; i++)
             dic[i] = NULL;
     }
 };

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

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

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

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

 private:
     TrieNode* root;
 };

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