Simple In-Place Quicksort in C (Just programming practice)

qsort.c

#include <cstdio>
#include <cstdlib>
#include <ctime>

void sort(int * a, size_t n) {
	if (n < 2)
		return;
	int p = a[n/2];
	int *l = a;
	int *r = a + n-1;
	while (l <= r) {
		if (*l < p)
			l++; 
		else if (*r > p)
			r--;
		else {
			int t = *l;
			*l++ = *r;
			*r-- = t;
		}
	}
	sort(a, r - a + 1);
	sort(l, a + n - l);
}


int main() {

	const size_t N = 20;
	int a[N]; 
	srand(time(0));

	// create a array of N random numnbers
	for (size_t i = 0; i < N; ++i) 
		a[i] = rand() % 100;

	// print the array
	printf("original: ");
	for (size_t i = 0; i < N; ++i)
		printf("%d ", a[i]);
	putchar('\n');	

	// sort the array
	sort(a, N);

	// print the array again
	printf("sorted: ");
	for (size_t i = 0; i < N; ++i)
		printf("%d ", a[i]);
	putchar('\n');

	return 0;
}