c++实现快速排序（优化版本）

#include<iostream>
using namespace std;

//交换两个元素
void Swap_Elem(int *arr, int first, int second)
{
	int temp = arr[first];
	arr[first] = arr[second];
	arr[first] = temp;
}

//将元素移动到正确位置
int Patition(int *arr, int low, int high)
{
	//三数取中，确保枢轴不是最小或者最大来提高算法效率
	int mid = high / 2; //计算数组中间元素下标
	if (arr[low] > arr[high])
	{
		Swap_Elem(arr, low, high);
	}
	if (arr[mid] > arr[high])
	{
		Swap_Elem(arr, mid, high);
	}
	if (arr[mid] > arr[low])
	{
		//使数组第一个下标low作为枢轴
		Swap_Elem(arr, mid, low);
	}
	int pivot = arr[low];
	//从数组的两端交替向中间扫描
	while (low < high)
	{
		while (low < high && arr[high] >= pivot)
		{
			high--;
		}
		arr[low] = arr[high];
		while (low < high && arr[low] <= pivot)
		{
			low++;
		}
		arr[high] = arr[low];
	}
	arr[low] = pivot;
	return low;
}


//快速排序
void Quick_Sort(int *arr, int low, int high)
{
	int pivot;
	while (low < high)
	{
		pivot = Patition(arr, low, high);
		Quick_Sort(arr, low, pivot - 1);
		//Quick_Sort(arr, pivot + 1, high); //原递归
		low = pivot + 1; //尾递归
	}
}


int main()
{
	int *arr = new int[10];
	for (int i = 0, num = 11; i < 10; i++, num--)
	{
		arr[i] = num;
	}
	cout << "排序前：" << endl;
	for (int i = 0; i < 10; i++)
	{
		cout << arr[i] << "\t";
	}
	cout << endl;
	Quick_Sort(arr, 0, 9);
	cout << "排序后：" << endl;
	for (int i = 0; i < 10; i++)
	{
		cout << arr[i] << "\t";
	}
	system("pause");
	return 0;
}