Trie

字典树

 1 class Trie {

 2     public:

 3         Trie() {

 4             root = new Node();

 5         }

 6 

 7         ~Trie() {

 8             destroy(root);

 9         }

10 

11         void insert(string word) {

12             Node* next = root;

13             for (int i = 0; i < word.length(); ++i) {

14                 if (next->next[word[i] - 'a'] == NULL) {

15                     next->next[word[i] - 'a'] = new Node();

16                 }

17                 next = next->next[word[i] - 'a'];            

18             }

19             next->val++; // 只要最尾个字符的位置计数

20         }

21 

22         int search(string word) {

23             Node* next = root;

24             int i = 0;

25             for (; i < word.length() && next != NULL; ++i) {

26                 next = next->next[word[i] - 'a'];

27             }

28             if (i == word.length() && next != NULL) {

29                 return next->val;

30             } else {

31                 return 0;

32             }    

33         }

34 

35     private:

36         struct Node {

37             int val;

38             Node *next[26];

39             Node(): val(0) {

40                 memset(next, 0, sizeof(Node*) * 26);

41             }

42         };

43 

44         void destroy(Node* p) {

45             if (p == NULL) return;

46             for (int i = 0; i < 26; ++i) {

47                 destroy(p->next[i]);

48             }

49             delete p;

50         }

51         Node* root;    

52 };