hoare_qsort.c

#include <stdio.h>
#include <stdlib.h>

void print_int_array(int ar[], size_t size) {
	int i;
	for (i = 0; i < size; i++)
		(i + 1) < size ? printf("%d, ", ar[i]): printf("%d\n", ar[i]);
}

void swap(int *x, int *y) {
	int tmp = *x;
	*x = *y;
	*y = tmp;
}

int partition(int ar[], int left, int right) {
	int pivot = ar[right];
	int lo = left, hi = right;
	while (1) {
		for(; ar[lo] < pivot; lo++)
			;
		for(; ar[hi] > pivot; hi--)
			;
		if (lo >= hi)
			return hi;
		swap(&ar[lo], &ar[hi]);
	}
}

void quick_sort(int ar[], int left, int right) {
	if (left < right) {
		int p = partition(ar, left, right);
		quick_sort(ar, left, p - 1);
		quick_sort(ar, p, right);
	}
}


int main(void) {
	int ar[] = {1, 3, 2, 4, 6, 5, 7};
	size_t size = sizeof(ar) / sizeof(ar[0]);
	puts("Before sort");
	print_int_array(ar, size);
	quick_sort(ar, 0, size - 1);
	puts("After sort");
	print_int_array(ar, size);
	return (0);
}