#include <stdio.h>

int partition(int v[], int p, int r)
{
    int i, j, tmp;

    for (i = j = p; j < r; ++j) {
        if ( v[j] < v[r] ) {
            tmp  = v[i];
            v[i] = v[j];
            v[j] = tmp;
            i++;
        }
    }
    
    tmp  = v[i];
    v[i] = v[r];
    v[r] = tmp;

    return i;
}

void quicksort(int v[], int p, int r)
{
    int q;
    if (p < r) {
        q = partition(v, p, r);
        quicksort(v, p, q-1);
        quicksort(v, q+1, r);
    }
}

int main()
{
    int i;
    int v[6] = {3, 4, 1, 2, 6, 5};
    
    for (i = 0; i < 6; ++i)
        printf("%d ", v[i]);
    printf("\n");
    
    quicksort(v, 0, 5);

    for (i = 0; i < 6; ++i)
        printf("%d ", v[i]);
    printf("\n");

    return 0;
}