方法一：

int Partition(int A[], int low, int high){
    int pivot = A[low];
    while(low < high){
        while(low < high && A[high] >= pivot) -- high;
        A[low] = A[high];
        while(low < high && A[low] <= pivot) ++ low;
        A[high] = A[low];
    }
    A[low] = pivot;
    return low;
}

void quick_sort(int A[], int low, int high){
    if(low < high){
        int pivotpos = Partition(A, low, high);
        quick_sort(A, low, pivotpos - 1);
        quick_sort(A, pivotpos + 1, high);
    }
}

方法二：

void quick_sort(int q[], int l, int r)
{
    if (l >= r) return;

    int i = l - 1, j = r + 1, x = q[l + r >> 1];
    while (i < j)
    {
        do i ++ ; while (q[i] < x);
        do j -- ; while (q[j] > x);
        if (i < j) swap(q[i], q[j]);
    }
    quick_sort(q, l, j), quick_sort(q, j + 1, r);
}

方法三：

void quick_sort(int q[], int l, int r)
{
    if (l >= r) return;

    int i = l, j = r, x = q[l];
    while (i < j)
    {
        while (q[i] < x) i ++;
        while (q[j] > x) j --;
        if (i < j) swap(q[i], q[j]);
    }
    quick_sort(q, l, j), quick_sort(q, j + 1, r);
}