[hihoCoder] Trie树

This is a application of the Trie data structure, with minor extension. The critical part in this problem is to count all the words that have a particualr prefix and the problem has given nice hints to make this extension.

Two functions require to be implemented: add a word to the Trie and search the Trie for all words with a particular prefix.

The code is as follows.

If you are not familiar with Trie, you may refer to this solution first to get the basic idea of it.

 #include <iostream>

 using namespace std;

 class TrieNode {
 public:
     int count;
     TrieNode* children[];
     TrieNode() {
         count = ;
         for (int i = ; i < ; i++)
             children[i] = NULL;
     }
 };

 class Dictionary {
 public:
     Dictionary() {
         root = new TrieNode();
     }

     void insert(char* word) {
         TrieNode* run = root;
         for (int i = ; word[i]; i++) {
             if (!(run -> children[word[i] - 'a']))
                 run -> children[word[i] - 'a'] = new TrieNode();
             run = run -> children[word[i] - 'a'];
             run -> count++;
         }
     }

     int search(char* prefix) {
         TrieNode* run = root;
         for (int i = ; prefix[i]; i++) {
             if (run)
                 run = run -> children[prefix[i] - 'a'];
             else break;
         }
         if (!run) return false;
         return run -> count;
     }

 private:
     TrieNode* root;
 };

 int main(void) {
     int dictSize;
     while (scanf("%d", &dictSize) != EOF) {
         Dictionary dictionary;
         char word[];
         for (int i = ; i < dictSize; i++) {
             scanf("%s", word);
             dictionary.insert(word);
         }
         int querySize;
         scanf("%d", &querySize);
         char prefix[];
         for (int i = ; i < querySize; i++) {
             scanf("%s", prefix);
             printf("%d\n", dictionary.search(prefix));
         }
     }
     return ;
 }