快排的一种相当简单但不算最快的实现方式

void quicksort(int v[], int n)
{
    int i, last;
    if (n <= 1) /* nothing to do */
        return;
    swap(v, 0, rand() % n);
    last = 0;
    for (i = 1; i < n; i++)
        if (v[i] < v[0])
            swap(v, ++last, i);
    swap(v, 0, last);
    quicksort(v, last);
    quicksort(v+last+1, n-last-1);
}

/* swap: interchage v[i] and v[j] */
void swap(int v[], int i, int j)
{
    int temp;
    temp = v[i];
    v[i] = v[j];
    v[j] = temp;
}