Implement Trie

Source

• lintcode: Implement Trie

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

Example
insert("lintcode")
search("code") // return false
startsWith("lint") // return true
startsWith("linterror") // return false
insert("linterror")
search("lintcode) // return true
startsWith("linterror") // return true
Note
You may assume that all inputs are consist of lowercase
letters a-z.

Java

/**
 * Your Trie object will be instantiated and called as such:
 * Trie trie = new Trie();
 * trie.insert("lintcode");
 * trie.search("lint"); will return false
 * trie.startsWith("lint"); will return true
 */
class TrieNode {
    // Initialize your data structure here.
    TrieNode[] children;
    boolean isEndOfWord;

    public TrieNode() {
        this.children = new TrieNode[26];
        this.isEndOfWord = false;
    }
}

public class Solution {
    private TrieNode root;

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

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

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

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