class Trie {
private:
    vector<Trie*>children;
    bool isEnd;
    Trie* searchPrefix(string prefix) {
        Trie* node = this;
        for(char c : prefix) {
            c -= 'a';
            if(node->children[c] == nullptr) {
                return nullptr;
            }
            node = node->children[c]; // 下一个结点
        }
        return node;
    }

public:
    /** Initialize your data structure here. */
    Trie() : children(26), isEnd(false) {}
    
    /** Inserts a word into the trie. */
    void insert(string word) {
        Trie* node = this;
        for(char c : word) {
            c -= 'a';
            if(node->children[c] == nullptr) {
                node->children[c] = new Trie();
            }
            node = node->children[c];
        }
        node->isEnd = true;
    }
    
    /** Returns if the word is in the trie. */
    bool search(string word) {
        Trie* node = this->searchPrefix(word);
        return node != nullptr && node->isEnd;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    bool startsWith(string prefix) {
        return this->searchPrefix(prefix) != nullptr;
    }
};

/**
 * Your Trie object will be instantiated and called as such:
 * Trie* obj = new Trie();
 * obj->insert(word);
 * bool param_2 = obj->search(word);
 * bool param_3 = obj->startsWith(prefix);
 */