Implementation of Single-Pivot Quick Sorting.

quick_sort.c

/**
 * Copyright 2014 Gagarine Yaikhom (MIT License)
 *
 * Implementation of Single-Pivot Quick Sorting.
 */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void print_array(const int *a, int size) {
    int i;
    for (i = 0; i < size; ++i)
	printf("%d ", a[i]);
    printf("\n");
}

void quick_sort(int *a, int size) {
    int i, j, t, pivot;
    if (size < 2)
	return;
    pivot = a[rand() % size];
    i = 0;
    j = size - 1;
    while (i < j) {
	while (a[i] < pivot) ++i;
	while (a[j] > pivot) --j;
	if (i < j) {
	    t = a[j];
	    a[j] = a[i];
	    a[i] = t;
	}
    }
    quick_sort(a, i);
    quick_sort(&a[i + 1], size - i - 1);
}

int main(void) {
    int a[] = {5, 3, 8, 2, 7, 6, 9}, size;
    size = sizeof(a) / sizeof(a[0]);
    printf("Unsorted: ");
    print_array(a, size);
    srand(time(0));
    quick_sort(a, size);
    printf("  Sorted: ");
    print_array(a, size);
    return 0;
}