// Function prototype
void arraycopy(int source[], int sourceStartIndex,
  int target[], int targetStartIndex, int length);

void merge(int list1[], int list1Size,
  int list2[], int list2Size, int temp[]);

/* The function for sorting the numbers */
void mergeSort(int list[], int arraySize)
{
  if (arraySize > 1)
  {
    // Merge sort the first half
    int *firstHalf = new int[arraySize / 2];
    arraycopy(list, 0, firstHalf, 0, arraySize / 2);
    mergeSort(firstHalf, arraySize / 2);

    // Merge sort the second half
    int secondHalfLength = arraySize - arraySize / 2;
    int *secondHalf = new int[secondHalfLength];
    arraycopy(list, arraySize / 2, secondHalf, 0, secondHalfLength);
    mergeSort(secondHalf, secondHalfLength);

    // Merge firstHalf with secondHalf
    merge(firstHalf, arraySize / 2, secondHalf, secondHalfLength,
      list);

    delete [] firstHalf;
    delete [] secondHalf;
  }
}

void merge(int list1[], int list1Size,
  int list2[], int list2Size, int temp[])
{
  int current1 = 0; // Current index in list1
  int current2 = 0; // Current index in list2
  int current3 = 0; // Current index in temp

  while (current1 < list1Size && current2 < list2Size)
  {
    if (list1[current1] < list2[current2])
      temp[current3++] = list1[current1++];
    else
      temp[current3++] = list2[current2++];
  }

  while (current1 < list1Size)
    temp[current3++] = list1[current1++];

  while (current2 < list2Size)
    temp[current3++] = list2[current2++];
}

void arraycopy(int source[], int sourceStartIndex,
  int target[], int targetStartIndex, int length)
{
  for (int i = 0; i < length; i++)
  {
    target[i + targetStartIndex] = source[i + sourceStartIndex];
  }
}