import java.util.HashMap;

public class TwoSumArray {
    public int[] twoSum(int[] nums, int target) {
        HashMap<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            int complement = target - nums[i];
            if (map.containsKey(complement)) {
                return new int[]{map.get(complement), i};
            }
            map.put(nums[i], i);
        }
        return new int[]{}; // no solution
    }

    public static void main(String[] args) {
        TwoSumArray obj = new TwoSumArray();
        int[] nums = {2, 7, 11, 15};
        int target = 9;

        int[] result = obj.twoSum(nums, target);

        System.out.print("Indices: ");
        for (int i : result) {
            System.out.print(i + " ");
        }
    }
}