TwoSum.java

/*
int[] nums = {2, 7, 11, 15};
int target = 9;
Output should be the indices [0, 1] because nums[0] + nums[1] = 2 + 7 = 9.
*/


import java.util.HashMap;
import java.util.Map;

public class TwoSum {
 public static int[] twoSum(int[] nums, int target) {
 Map<Integer,Integer> map = new HashMap<>();
 for(int i = 0; i < nums.length;i++){
 int value = target - nums[i];
 if(map.containsKey(value)){
 return new int[] {map.get(value),i};
 }
 map.put(nums[i],i);
 }

 throw new IllegalArgumentException("No two sum solution");
 }

 public static void main(String[] args) {
 int[] nums = {2, 5, 15, 7};
 int target = 9;
 int [] result = twoSum(nums,target);
 System.out.println(result[0] + "," +result[1]);
 }
}