class TrieNode {
public:
    // Initialize your data structure here.
    TrieNode* next[26];
    bool valid;
    TrieNode() {
        memset(next, NULL, sizeof(next));
        valid = false;
    }
};

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

    // Inserts a word into the trie.
    void insert(string word) {
        if (word.length() <= 0) {
            return;
        }
        int len = word.length();
        TrieNode* p = root;
        for (int i = 0; i < len; i++) {
            if (p->next[word[i] - 'a'] == NULL) {
                p->next[word[i] - 'a'] = new TrieNode();
                p = p->next[word[i] - 'a'];
            }
            else {
                p = p->next[word[i] - 'a'];
            }
        }
        p->valid = true;
    }

    // Returns if the word is in the trie.
    bool search(string word) {
        if (word.length() <= 0) {
            return false;
        }
        int len = word.length();
        TrieNode* p = root;
        for (int i = 0; i < len; i++) {
            if (p->next[word[i] - 'a'] != NULL) {
                p = p->next[word[i] - 'a'];
            }
            else {
                return false;
            }
        }
        if (p->valid) {
            return true;
        }
        else {
            return false;
        }
    }

    // Returns if there is any word in the trie
    // that starts with the given prefix.
    bool startsWith(string prefix) {
        if (prefix.length() <= 0) {
            return false;
        }
        int len = prefix.length();
        TrieNode* p = root;
        for (int i = 0; i < len; i++) {
            if (p->next[prefix[i] - 'a'] == NULL) {
                return false;
            }
            else {
                p = p->next[prefix[i] - 'a'];
            }
        }
        return true;
    }

private:
    TrieNode* root;
};

// Your Trie object will be instantiated and called as such:
// Trie trie;
// trie.insert("somestring");
// trie.search("key");