public class Solution {
    public int[] twoSum(int[] numbers, int target) {
        HashMap<Integer, Integer> complements = new HashMap<>();
        for (int i = 0; i < numbers.length; i++) {
            int current = numbers[i];
            int complement = target - current;
            if (complements.containsKey(complement)) {
                return new int[] { complements.get(complement), i };
            }
            complements.put(current, i);
        }
        return new int[]{};
    }
}