_144startsWith.java

public class _144startsWith {
    static class Node{
        Node[] children = new Node[26];
        boolean eow;
        public Node(){
            for(int i=0;i<children.length;i++){
                children[i]=null;
            }
        }
    }
    public static Node root = new Node();
    public static void insert(String word){
        int level = 0;
        int len = word.length();
        int idx = 0;

        Node curr = root;
        for(;level<len;level++){
            idx=word.charAt(level)-'a';
            if(curr.children[idx]==null){
                curr.children[idx] = new Node();
            }
            curr=curr.children[idx];
        }
        curr.eow=true;
    }
    public static boolean search(String key){
        int level = 0;
        int len = key.length();
        int idx = 0;

        Node curr = root;
        for(;level<len;level++){
            idx=key.charAt(level)-'a';
            if(curr.children[idx]==null){
                return false;
            }
            curr=curr.children[idx];
        }
        return curr.eow==true;
    }
    public static boolean startsWith(String prefix){
        Node curr= root;
        for(int i=0;i<prefix.length();i++){
            int idx = prefix.charAt(i)-'a';
            if(curr.children[idx]==null){
                return false;
            }
            curr=curr.children[idx];
        }
        return true;
    }
    public static void main(String[] args) {
        String words[] = {"apple","app","mango","man","woman"};
        String prefix = "app";
        String prefix2 = "moon";
        for(int i =0;i<words.length;i++){
            insert(words[i]);
        }
        System.out.println(startsWith(prefix));
        System.out.println(startsWith(prefix2));
    }
}