LeetCode 677. 键值映射
一个简单的Tire树模板题，存个档
1 class MapSum { 2 3 struct TrieNode { 4 TrieNode* next[26]; 5 int val; 6 TrieNode() { 7 for(int i = 0; i < 26; i++) 8 this->next[i] = NULL; 9 this->val = 0; 10 } 11 }; 12 13 public: 14 MapSum() { 15 root = new TrieNode(); 16 } 17 18 void insert(string key, int val) { 19 int delta = val; 20 if(cnt.count(key)) 21 delta -= cnt[key]; 22 cnt[key] = val; 23 TrieNode* node = root; 24 for(auto c : key) { 25 if(node->next[c - 'a'] == NULL) 26 node->next[c - 'a'] = new TrieNode(); 27 node = node->next[c - 'a']; 28 node->val += delta; 29 } 30 } 31 32 int sum(string prefix) { 33 TrieNode* node = root; 34 for(auto c : prefix) { 35 if(node->next[c - 'a'] == NULL) 36 return 0; 37 node = node->next[c-'a']; 38 } 39 return node->val; 40 } 41 private: 42 unordered_map<string, int> cnt; 43 TrieNode* root; 44 };
