C++代码：

void QuickSort(int a[], int left, int right)
{
    if (left<right)
    {
        int pivotpos = Partition(a, left, right);
        QuickSort(a, left, pivotpos-1);
        QuickSort(a, pivotpos+1 ,right);
    }
}

int Partition(int a[], int low, int high)
{
    int pivot = median3(a, low ,high);
    int i = low;
    int j = high-1;
    int temp;
    while (1)
    {
        while (i<j && a[i]<pivot)
        {
            ++i;
        }
        while (i<j && a[j]>pivot)
        {
            --j;
        }
        if (i<j)
        {
            temp = a[i];
            a[i] = a[j];
            a[j] = temp;
            ++i;
            --j;
        }
        else
            break;
    }
    if (a[i]>pivot)
    {
        a[high] = a[i];
        a[i] = pivot;
    }
    return i;
}

//取最左、最右和中间三个值作比较，使最左边存三者中最小，中间处存三者中最大
//并返回最右值作为基准值
int median3(int a[], int left, int right)
{
    int k = left;
    int mid = (left+right)/2;
    int temp;
    if (a[mid]<a[k])
    {
        k = mid;
    }
    if (a[right]<a[k])
    {
        k = right;
    }
    if (k!=left)
    {
        temp = a[k];
        a[k] = a[left];
        a[left] =temp;
    }
    if (a[right]>a[mid])
    {
        temp = a[right];
        a[right] = a[mid];
        a[mid] = temp;
    }
    return a[right];
}


不理解的地方就是Partition函数while（1）循环跳出后的那个if语句，它只做大于判断，那其它情况呢？