LeetCode[208] Implement Trie (Prefix Tree)

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

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

class TrieNode {
public:
	// Initialize your data structure here.
	TrieNode(char cc) : c(cc), isLeaf(false) {
		memset(child, NULL, sizeof(child));
	}
	TrieNode() : isLeaf(false) {
		memset(child, NULL, sizeof(child));
	}
	char c;
	bool isLeaf;
	TrieNode* child[26];
};

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

	// Inserts a word into the trie.
	void insert(string word) {
		TrieNode* node = root;
		string::iterator it = word.begin();
		while (it != word.end()) {
			if (node->child[*it - 'a'] == NULL)
				node->child[*it - 'a'] = new TrieNode(*it);
			node = node->child[*it - 'a'];
			++it;
		}
		node->isLeaf = true;
	}

	// Returns if the word is in the trie.
	bool search(string word) {
		TrieNode* node = root;
		string::iterator it = word.begin();
		while (it != word.end()) {
			if (node->child[*it - 'a'] == NULL)
				return false;
			node = node->child[*it - 'a'];
			++it;
		}
		if (node->isLeaf)
			return true;
		return false;
	}

	// Returns if there is any word in the trie
	// that starts with the given prefix.
	bool startsWith(string prefix) {
		TrieNode* node = root;
		string::iterator it = prefix.begin();
		while (it != prefix.end()) {
			if (node->child[*it - 'a'] == NULL)
				return false;
			node = node->child[*it - 'a'];
			++it;
		}
			return true;
	}

private:
	TrieNode* root;
};

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