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：

 1 class Trie {
 2 public:
 3     int passed; // 记录经过这个节点的字符串数量
 4     int ends;   // 记录有多少个字符串以这个节点结尾
 5     unordered_map< char, Trie* > nxt;
 6     
 7     /** Initialize your data structure here. */
 8     Trie() {
 9         passed = 0;
10         ends = 0;
11     }
12     
13     /** Inserts a word into the trie. */
14     void insert(string word) {
15         Trie* p = this;
16         for(int i = 0; i < word.size(); ++i) {
17             if(p->nxt.find(word[i]) == p->nxt.end()) {
18                 p->nxt[word[i]] = new Trie();
19             }
20             ++p->passed;
21             p = p->nxt[word[i]];
22         }
23         ++p->ends;
24     }
25     
26     /** Returns if the word is in the trie. */
27     bool search(string word) {
28         Trie* p = this;
29         for(int i = 0; i < word.size(); ++i) {
30             if(p->nxt.find(word[i]) == p->nxt.end()) return false;
31             p = p->nxt[word[i]];
32         }
33         return p->ends != 0;
34     }
35     
36     /** Returns if there is any word in the trie that starts with the given prefix. */
37     bool startsWith(string prefix) {
38         Trie* p = this;
39         for(int i = 0; i < prefix.size(); ++i) {
40             if(p->nxt.find(prefix[i]) == p->nxt.end()) return false;
41             p = p->nxt[prefix[i]];
42         }
43         return true;
44     }
45 };
46 
47 /**
48  * Your Trie object will be instantiated and called as such:
49  * Trie* obj = new Trie();
50  * obj->insert(word);
51  * bool param_2 = obj->search(word);
52  * bool param_3 = obj->startsWith(prefix);
53  */

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