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:
    bool isWord;
    vector<TrieNode* >child;
    TrieNode():isWord(false),child(vector<TrieNode* >(26,nullptr)){};
};
class Trie {
public:
    /** Initialize your data structure here. */
    Trie(){
        root=new TrieNode();
    }
    
    /** Inserts a word into the trie. */
    void insert(string word) {
        TrieNode* temp=root;
        for(int i=0;i<word.length();i++){
            int c=word[i]-'a';
            if(temp->child[c]==NULL)temp->child[c]=new TrieNode();
            temp=temp->child[c];
        }
        temp->isWord=true;
    }
    
    /** Returns if the word is in the trie. */
    bool search(string word) {
        TrieNode* temp=root;
        for(int i=0;i<word.length();i++){
            int c=word[i]-'a';
            if(temp->child[c]==NULL)return false;
            temp=temp->child[c];
        }
        return temp->isWord;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    bool startsWith(string prefix) {
        TrieNode* temp=root;
        for(int i=0;i<prefix.length();i++){
            int c=prefix[i]-'a';
            if(temp->child[c]==NULL)return false;
            temp=temp->child[c];
        }
        return true;
    }
private:
    TrieNode* root;
};

/**
 * 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);
 */