Thread: Need help on this bitonic merge sort

So for my assignment I need to implement a recursive bitonic mergesort that takes the input array, size, output array, and output_asc where true ascends and false descends.
There is a helper function in the test runner so I don't need to allocate extra memory for the left half and right half so I'm lost in the recursion when calling mergesort for left half and right half.
Can someone check my code to see what I'm doing wrong?

Code:

#include<iostream>
void merge(int *input, int size, int *output, bool output_asc)
{
  int mid = size / 2;
  int i = 0;
  int j = size - 1;
  int k = 0;

  if (output_asc) {
    while (i < mid && j >= mid) {
      if (input <= input[j])
        output[k++] = input[i++];
      else
        output[k++] = input[j--];
    }
  } else {
    while (i < mid && j >= mid) {
      if (input >= input[j])
        output[k++] = input[i++];
      else
        output[k++] = input[j--];
    }
  }

  // Copy the remaining elements from the first section
  while (i < mid) {
    output[k++] = input[i++];
  }

  // Copy the remaining elements from the second section
  while (j >= mid) {
    output[k++] = input[j--];
  }
}

void mergesort(int *input, int size, int *output, bool output_asc)
{
  if (size == 0)
    return;
  else if (size == 1) {
    output[0] = input[0];
  } else {
    int mid = size / 2;
    mergesort(input, mid, output, true);
    mergesort(input + mid, size - mid, output + mid, false);

    for (int i = 0; i < size; ++i)
      input = output;

    merge(input, size, output, output_asc);
  }
}

int main()
{
  // Example usage
  const int size = 8;
  int input = { 4, 2, 7, 1, 5, 8, 3, 6 };
  int output;

  // Ascending order
  mergesort(input, size, output, true);
  std::cout << "Sorted in ascending order: ";
  for (int i = 0; i < size; i++) {
    std::cout << output << " ";
  }
  std::cout << std::endl;

  // Descending order
  mergesort(input, size, output, false);
  std::cout << "Sorted in descending order: ";
  for (int i = 0; i < size; i++) {
    std::cout << output << " ";
  }
  std::cout << std::endl;

  return 0;

}

Firstly, when you paste code, you need to paste it as plain text, not text with a bunch of formatting in it.

As for your problem, instead of this:

Code:

        mergesort(input,       mid,        output,       true);
        mergesort(input + mid, size - mid, output + mid, false);

try this:

Code:

        mergesort(input,       mid,        output,        output_asc);
        mergesort(input + mid, size - mid, output + mid, !output_asc);