leetcode208.java

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

public class Trie {
    private TrieNode root;

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

    // Inserts a word into the trie.
    public void insert(String word) {
        TrieNode tmp = root;
        for(int i = 0; i < word.length(); i++){
            char c = word.charAt(i);
            if(tmp.children[c - 'a'] == null){
                tmp.children[c - 'a'] = new TrieNode();
            }
            tmp = tmp.children[c - 'a'];
        }
        tmp.isWord = true;
    }

    // Returns if the word is in the trie.
    public boolean search(String word) {
        TrieNode tmp = root;
        for(int i = 0; i < word.length(); i++){
            char c = word.charAt(i);
            if(tmp.children[c - 'a'] == null)
                return false;
            tmp = tmp.children[c - 'a'];
        }
        return tmp.isWord;
    }

    // Returns if there is any word in the trie
    // that starts with the given prefix.
    public boolean startsWith(String prefix) {
        TrieNode tmp = root;
        for(int i = 0; i < prefix.length(); i++){
            char c = prefix.charAt(i);
            if(tmp.children[c - 'a'] == null)
                return false;
            tmp = tmp.children[c - 'a'];
        }
        return true;
    }
}

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