快速排序c++

优化：在划分的时候使用左右同时移动，找到i大于基准点的数和j小于基准点的数(在i<j)的情况下，互换位置，到i>=j，查看r[i]的大小，大于基准点说明i-1为想要位置，否则就是i。

#include<iostream>
using namespace std;
int Partition2(int r[], int low, int high)
{
	int i = low, j = high, pivot = r[low];
	while (i < j)
	{
		while (i<j&&r[j]>pivot) j--;
		while (i < j&&r[i] <= pivot) i++;
		if (i < j)
		{
			int t = r[j];
			r[j++] = r[i];
			r[i++] = t;
		}
	}
	if (r[i] > pivot)
	{
		int t = r[low];
		r[low] = r[i-1];
		r[i-1] = t;
		return i - 1;
	}
	else 
	{
		int t = r[low];
		r[low] = r[i];
		r[i] = t;
		return i;
	}
}
void QuickSort(int r[], int low, int high)
{
	if (low < high)
	{
		int mid = Partition2(r, low, high);
		QuickSort(r, low, mid-1);
		QuickSort(r, mid + 1, high);
	}
}
int main() {
	int r[5] = {1,5,3,4,2};
	QuickSort(r, 0, 4);
	for (int i = 0; i < 5; i++)
	{
		cout << r[i] << " ";
	}
	return 0;
}