#include <stdio.h>
#include <stdlib.h>   /* for qsort */

int comp(const void *p1, const void *p2);

int main()
{
	int a[] = {1, 3, 0, 2, 5};
	const size_t n = sizeof a / sizeof a[0];
	const int *p;

	qsort(a, n, sizeof a[0], comp);   /* last arg is pointer to function */

	for (p = a; p < a + n; ++p) {
		printf("%d\n", *p);
	}

	return EXIT_SUCCESS;
}

int comp(const void *p1, const void *p2)  /* sort in increasing numeric order */
{
	const int i = *(const int *)p1;   /* can't dereference void * */
	const int j = *(const int *)p2;

	if (i < j) {
		return -1;
	}

	if (i > j) {
		return 1;
	}

	return 0;
}