兩個輔助函式：

// 生成區間內的隨機整數
int RandInRange(int s, int e, unsigned seed=time_t(0))
{ 
    srand(seed);
    return rand()%(e-s)+s;
}

void Swap(int& a, int& b)
{
    int tmp = a; a = b; b = tmp;
}

分割槽函式：

int partition(int seq[], int len, int start, int end)
{
    if (seq == NULL || len <= 0 || start < 0
 
 || end >= len)
        throw new exception("Invalid parameters");

    int pivot = RandInRange(start, end);
    Swap(seq[pivot], seq[end]);

    int small = start - 1;
    for (int i = start; i < end; ++i)
    {
        if (seq[i] < seq[end])  
        {
            ++small;
            if
 
 (small != i)
                Swap(seq[small], seq[i]);
        }
    }
    ++small;
    Swap(seq[end], seq[small]);
    return small;
}

主調函式，由遞迴結構定義：

void qsort(int seq[], int len, int start, int end)
{
    if (start == end)
        return;
    int idx = partition(seq, len, start, end);
    if (idx > start)
        qsort(seq, len
 
, start, idx-1);
    if (idx < end)
        qsort(seq, len, idx+1, end);
}