class Solution {
    public int[] twoSum(int[] nums, int target) {
        HashMap<Integer, Integer> h = new HashMap<>();

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