CODEWITHSUNDEEP
calgorithmsortingfunction-pointersvoid-pointers
user2947605
user2947605

Reputation:

Writing generic mergeSort in C, can't assign value to void*

I am trying to code up a "generic" mergeSort in C:

void mergeSort(void *arr, int begin, int end,int size,
    int (*comp)(void *, void *));

But since you need a holder/temp array, it becomes a bit tricky. I am not sure how to assign values to that array, since I created it as a void * array:

int mid = (begin + end) / 2;
int len = end - begin + 1;
void *pom = malloc(len*size);

But I can't assign values to that array, is there a way around it?

i = begin, j = mid + 1, k = 0;
while (i <= mid && j <= end)
    **pom[k++]** = ((*comp)((char*)arr + i*size, (char *)arr + j*size) <= 0) ? arr[i] : arr[j];
while (i <= mid)
    **pom[k++]** = arr[i++];
while (j <= end)
    **pom[k++]** = arr[j++];

the bold lines give off an error.

Upvotes: 1

Views: 519

Answers (1)

Sorin
Sorin

Reputation: 11968

Yes, you need to copy size bytes.

So **pom[k++]** = arr[i++]; becomes memcpy(pom + size*(k++), arr+size*(i++), size); and similar for all the others.

Upvotes: 2

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