Trie

字典树

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

         ~Trie() {
             destroy(root);
         }

         void insert(string word) {
             Node* next = root;
             for (int i = ; i < word.length(); ++i) {
                 if (next->next[word[i] - 'a'] == NULL) {
                     next->next[word[i] - 'a'] = new Node();
                 }
                 next = next->next[word[i] - 'a'];
             }
             next->val++; // 只要最尾个字符的位置计数
         }

         int search(string word) {
             Node* next = root;
             int i = ;
             for (; i < word.length() && next != NULL; ++i) {
                 next = next->next[word[i] - 'a'];
             }
             if (i == word.length() && next != NULL) {
                 return next->val;
             } else {
                 return ;
             }
         }

     private:
         struct Node {
             int val;
             Node *next[];
             Node(): val() {
                 memset(next, , sizeof(Node*) * );
             }
         };

         void destroy(Node* p) {
             if (p == NULL) return;
             for (int i = ; i < ; ++i) {
                 destroy(p->next[i]);
             }
             delete p;
         }
         Node* root;
 };