Contact.java

import java.io.*;
import java.util.*;

public class Contact{
 public static List<Integer> contacts(List<List<String>> queries) {
 // Write your code here
 HashMap<String, Integer> map = new HashMap<String, Integer>();
 List<Integer> response = new ArrayList<>();
 for(int i=0; i < queries.size(); i++){
 List<String> query = queries.get(i);
 String action = query.get(0);
 String key = query.get(1);
 if( action == "add"){
 for (int j = 1; j <= key.length(); j++){
 String sub = key.substring(0, j);
 if (map.get(sub) == null){
 map.put(sub, 1);
 } else {
 map.put(sub, map.get(sub) + 1);
 }
 }
 }else if(action == "find"){
 if (map.get(key) == null){
 response.add(0);
 } else {
 response.add(map.get(key));
 }
 }
 }
 return response;
 }

 public static void main(String[] args) throws IOException {

 List<List<String>> queries = new ArrayList<>();
 List<String> query1 = new ArrayList<>();
 query1.add("add");
 query1.add("hack");
 queries.add(query1);
 List<String> query2 = new ArrayList<>();
 query2.add("add");
 query2.add("hackerrank");
 queries.add(query2);
 List<String> query3 = new ArrayList<>();
 query3.add("find");
 query3.add("hac");
 queries.add(query3);
 List<String> query4 = new ArrayList<>();
 query4.add("find");
 query4.add("hak");
 queries.add(query4);
 List<Integer> result = contacts(queries);
 System.out.println(result);
 }
}