public class Solution {

public int[] twoSUm(int[] numbers, int target) {

HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
int[] result = new int[2];

for (int i=0; i < numbers.length; i++) {
 if (map.containsKey(numbers[i])) {
  int index = map.get(numbers[i]);
  result[0] = index;
  result[1] = i;
  break;
 } else {
   map.put(target - numbers[i], i);
}
}

return result;
}
}

// O(1) - get and put operations of HashMap
// O(n)