TwoSumUnsorted.java

package com.sarvesh.javabasics;

import java.util.HashMap;
import java.util.Arrays; 

public class TwoSumUnsorted {

 public static void main(String[] args) {
 int[] arr = {7, 11, 2, 15};
 int target = 9;
 int[] result = twoSum(arr, target);
 System.out.println("Match found at indexes: " + Arrays.toString(result));
 }

 public static int[] twoSum(int[] nums, int target) {
 HashMap<Integer, Integer> num = new HashMap<>();

 for (int i = 0; i < nums.length; i++) {
 int currentNum = nums[i];
 int complement = target - currentNum;
 
 if (num.containsKey(complement)) {
 int complementIndex = num.get(complement);
 return new int[] { complementIndex, i };
 }
 
 num.put(currentNum, i);
 }
 return new int[] {};
 }
}