Quick sort.

quick_sort.c

#include <stdio.h>

#define swap(x, y) { int tmp = x; x = y; y = tmp; }

void quick_sort(int n, int array[]) {
    if(n < 2) return;
    int i = 0;
    int j = n - 2;
    while(i <= j) {
        while(i <= j && array[i] <= array[n - 1]) ++i;
        while(j >= i && array[j] > array[n - 1]) --j;
        if(i < j) {
            swap(array[i], array[j]);
        }
    }
    swap(array[i], array[n - 1]);
    quick_sort(i, array);
    quick_sort(n - i, array + i);
}

#define test(...) \
{                                           \
    int array[] = { __VA_ARGS__ };          \
    int size = sizeof(array) / sizeof(int); \
    quick_sort(size, array);                \
    for(int i = 0; i < size; ++i) {         \
        printf("%d ", array[i]);            \
    }                                       \
    printf("\n");                           \
}

int main(void) {
    test(1, 2, 6, 9, 8, 3, 10, 7, 5, 4);
    test(7, 10, 2, 9, 1, 8, 5, 4, 6, 3);
    test(5, 10, 3, 8, 6, 4, 7, 1, 9, 2);
    test(3, 8, 10, 1, 9, 5, 7, 6, 2, 4);
    test(2, 1, 8, 5, 4, 10, 7, 6, 9, 3);
    test(6, 8, 3, 9, 5, 7, 2, 1, 10, 4);
    test(1, 2, 6, 5, 9, 4, 8, 3, 7, 10);
    test(1, 2, 8, 6, 5, 7, 10, 4, 3, 9);
    test(3, 5, 4, 6, 8, 2, 10, 9, 7, 1);
    test(9, 4, 3, 6, 1, 7, 2, 10, 8, 5);
    return 0;
}