Implement a trie with insert, search, and startsWith methods.

Notice

You may assume that all inputs are consist of lowercase letters a-z.

Have you met this question in a real interview?

Yes

Example

insert("lintcode")
search("code")
>>> false
startsWith("lint")
>>> true
startsWith("linterror")
>>> false
insert("linterror")
search("lintcode)
>>> true
startsWith("linterror")
>>> true

/**
 * Your Trie object will be instantiated and called as such:
 * Trie trie;
 * trie.insert("lintcode");
 * trie.search("lint"); will return false
 * trie.startsWith("lint"); will return true
 */
class TrieNode {
public:
    // Initialize your data structure here.
    TrieNode() {
        for (int i = 0; i < 26; ++i) {
            next[i] = NULL;
        }
        IsEnd = false;
    }
    TrieNode* next[26];
    bool IsEnd;
};

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

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

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

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

private:
    TrieNode* root;
};