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：

 1 class TrieNode {
 2 public:
 3     // Initialize your data structure here.
 4     TrieNode():isLeaf(false)
 5     {
 6         for(auto & t : dic){
 7             t = NULL;
 8         }
 9     }
10     TrieNode * dic[26];
11     bool isLeaf;
12 };
13
14 class Trie {
15 public:
16     Trie() {
17         root = new TrieNode();
18     }
19
20     // Inserts a word into the trie.
21     void insert(string word) {
22         TrieNode * p = root;
23         for(int i = 0; i < word.size(); ++i){
24             int index = word[i] - ‘a‘;
25             if(p->dic[index] == NULL)
26                 p->dic[index] = new TrieNode();
27             p = p->dic[index];
28         }
29         p->isLeaf = true;
30     }
31
32     // Returns if the word is in the trie.
33     bool search(string word) {
34         TrieNode * p = root;
35         for(int i = 0; i < word.size(); ++i){
36             int index = word[i] - ‘a‘;
37             if(p->dic[index] == NULL)
38                 return false;
39             p = p->dic[index];
40         }
41         return p->isLeaf;
42     }
43
44     // Returns if there is any word in the trie
45     // that starts with the given prefix.
46     bool startsWith(string prefix) {
47         TrieNode * p = root;
48         for(int i = 0; i < prefix.size(); ++i){
49             int index = prefix[i] - ‘a‘;
50             if(p->dic[index] == NULL)
51                 return false;
52             p = p->dic[index];
53         }
54         return true;
55     }
56
57 private:
58     TrieNode* root;
59 };
60
61 // Your Trie object will be instantiated and called as such:
62 // Trie trie;
63 // trie.insert("somestring");
64 // trie.search("key");