Implement Trie Tree，用memset做初始化

class TrieNode {
public:
    bool exist;
    TrieNode* children[26];
    TrieNode() {
        exist = false;
        memset(children, 0, sizeof(children));
    }
};

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

    void insert(string word) {
        TrieNode* cur = root;
        for(char c: word){
            if(cur->children[c-'a']==NULL) cur->children[c-'a'] = new TrieNode();
            cur = cur->children[c-'a'];
        }
        cur->exist = true;
    }

    // Returns if the word is in the trie.
    bool search(string word) {
        TrieNode* cur = root;
        for(char c: word){
            if(cur->children[c-'a']==NULL) return false;
            cur = cur->children[c-'a'];
        }
        return (cur->exist);
    }

    bool startsWith(string prefix) {
        TrieNode* cur = root;
        for(char c: prefix){
            if(cur->children[c-'a']==NULL) return false;
            cur = cur->children[c-'a'];
        }
        return true;
    }

private:
    TrieNode* root;
};

如果没有用memset，在有些编译器上不会给children赋初值。然后这个代码就run time error 了额....