Implement Trie Prefix Tree

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

Solution:

class TrieNode {
    boolean isLeaf;
    TrieNode[] next;
    // Initialize your data structure here.
    public TrieNode() {
        isLeaf = false;
        next = new TrieNode[26];
    }
}

public class Trie {
    private TrieNode root;

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

    // Inserts a word into the trie.
    public void insert(String word) {
        TrieNode cur = root;
        for(char c : word.toCharArray()){
            if(cur.next[c-'a']==null){
                cur.next[c-'a'] = new TrieNode();
            }
            cur = cur.next[c-'a'];
        }
        cur.isLeaf = true;
    }

    // Returns if the word is in the trie.
    public boolean search(String word) {
        TrieNode cur = root;
        for(char c : word.toCharArray()){
            if(cur.next[c-'a']==null){
                return false;
            }
            cur = cur.next[c-'a'];
        }
        return cur.isLeaf;
    }

    // Returns if there is any word in the trie
    // that starts with the given prefix.
    public boolean startsWith(String prefix) {
        TrieNode cur = root;
        for(char c : prefix.toCharArray()){
            if(cur.next[c-'a']==null){
                return false;
            }
            cur = cur.next[c-'a'];
        }
        return true;
    }
}

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