private static void mergesort(int[] items, int[] temp, 
                                int left, int right) {
    if (left == right) {
      return;
    }

    int mid = (left + right) / 2; 

    mergesort(items, temp, left, mid); 
    mergesort(items, temp, mid + 1, right); 

    merge(items, temp, left, mid, right);
  }

  private static void merge(int[] items, int[] temp, 
                            int left, int mid, int right) {

    for (int i = left; i <= right; i++) {
      temp[i] = items[i];// Copy subarray to temp
    }

    int i1 = left;
    int i2 = mid + 1;
    for (int curr = left; curr <= right; curr++) {
      if (i1 == mid + 1) { // Left subarray exhausted
        items[curr] = temp[i2++];
      } else if (i2 > right) { // Right subarray exhausted
        items[curr] = temp[i1++];
      } else if (temp[i1] <= temp[i2]) { // Get smaller value (COUNT THIS!)
        items[curr] = temp[i1++];
      } else {
        items[curr] = temp[i2++];
      }
    }
  }