array.c

#include <stddef.h>
#include <stdlib.h>

int *split_and_add(size_t si, const int arr[si], int n, size_t *so) {

      // initializing variables
      int left;
      int right;
      int *top_arr;
      int *bottom_arr;
      int *result = malloc(si * sizeof(int));

      // copies input arr[] over to use
      for (int i = 0; i < si; i++)
      {
          result[i] = arr[i];
      }

  while (n != 0)
  {
      if (si % 2 == 0)
      {
          left = si / 2;
          right = left;
          top_arr = malloc(left * sizeof(int));
          bottom_arr = malloc(right * sizeof(int));

          for (int i = 0; i < left; i++)
          {
              top_arr[i] = result[i];
              bottom_arr[i] = result[i+si/2];
          }
      }

      else
      {
          left = si / 2 + 1;
          right = left;
          top_arr = malloc(left * sizeof(int));
          bottom_arr = malloc(right * sizeof(int));
          top_arr[0] = 0;
          for (int i = 0; i < left; i++)
          {
              top_arr[i+1] = result[i];
              bottom_arr[i] = result[i+si/2];
          }
      }

      // add up both arrays
      for (int i = 0; i < left; i++)
      {
          result[i] = top_arr[i] + bottom_arr[i];
      }

      // get new value for array size and reduce count
      si = left;
      n--;
  }

      for (int i = 0; i < si; i++)
      {
        printf("%d ", result[i]);
      }
      printf("\n");
      printf("\n");
      *so = si;
      return result;
}