快速排序

void quicksort(int a[], int left, int right)
{
    if (left < right)
    {
        int low = left;
        int high = right;
        int key = a[left];

        while (low < high)
        {
            while (low < high && a[high] > key)
                high--;

            a[low] = a[high];

            while (low < high && a[low] < key)
                low++;

            a[high] = a[low];
        }

        a[low] = key;
        quicksort(a[], left, low-1);
        quicksort(a[], low+1, right);
    }
}