快速排序实现

#include <iostream>
#include <vector>
#include <cstdlib>
#include <ctime>
void Qsort(std::vector<int>& arr, int low, int high);//形参绝对不能用unsigned！
int Partition(std::vector<int>& arr, int low, int high);
int main(void)
{
	std::vector<int>arr(20);
	srand((unsigned int)time(nullptr));
	for (int i = 0; i != 20; ++i)
		arr[i] = (int)rand() % 100 + 1;
	for (int i = 0; i != 20; ++i)
		std::cout << arr[i] << ' ';
	std::cout << std::endl;
	Qsort(arr, 0, arr.size() - 1);
	for (int i = 0; i != 20; ++i)
		std::cout << arr[i] << ' ';
	std::cout << std::endl;
	return 0;
}
void Qsort(std::vector<int>& arr, int low, int high)
{
	int pivot;
	if (low < high)//随处可见的low<high，保证程序正确运行
	{
		pivot = Partition(arr, low, high);//计算杻枢
		Qsort(arr, low, pivot - 1);//杻枢已经归位，无需对其排序
		Qsort(arr, pivot + 1