leetcode@ [208] Implement Trie (Prefix Tree)

class TrieNode {
public:
    char var;
    bool isWord;
    TrieNode *next[26];
    TrieNode() {
        var = 0;
        this->isWord = false;
        for(auto &c : next) c = NULL;
    }
    TrieNode(char c) {
        var = c;
        this->isWord = false;
        for(auto &c : next) c = NULL;
    }
};

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

    // Inserts a word into the trie.
    void insert(string word) {
        TrieNode *p = root;
        for(auto &a : word) {
            int idx = a - ‘a‘;
            if(!p->next[idx]) p->next[idx] = new TrieNode();
            p = p->next[idx];
        }
        p->isWord = true;
    }

    // Returns if the word is in the trie.
    bool search(string word) {
        TrieNode *p = root;
        for(auto &a : word) {
            int idx = a - ‘a‘;
            if(!p->next[idx]) return false;
            p = p->next[idx];
        }
        return p->isWord;
    }

    // Returns if there is any word in the trie
    // that starts with the given prefix.
    bool startsWith(string prefix) {
        TrieNode *p = root;
        for(auto &a : prefix) {
            int idx = a - ‘a‘;
            if(!p->next[idx]) return false;
            p = p->next[idx];
        }
        return true;        
    }

private:
    TrieNode* root;
};

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