快排（C或C++实现）

一.

二.

时间复杂度O(nlogn）

 空间复杂度(O(logn))

不稳定   

三.

1.代码实现

#include<stdio.h>
int Partition(int* arr, int left, int right)
{
	int tmp = arr[left];
	while (left<right)
	{
		while (left<right&&tmp <=arr[right])
		{
			right--;
		}
		if (left == right)
		{
			break;
		}
		arr[left] = arr[right];
		while (left<right&&tmp > arr[left])
		{
			left++;
		}
		if (left == right)
		{
			break;
		}
		arr[right] = arr[left];
	}
	arr[left] = tmp;
	return left;
}

void Quick(int* arr, int left, int right)
{
	int par = Partition(arr, left, right);
	if (left < par - 1)
	{
		Quick(arr, left, par - 1);
	}
	if (par + 1 < right)
	{
		Quick(arr, par + 1, right);
	}
}
void Quick_Sort(int* arr, int len)
{
	Quick(arr, 0, len - 1);
}
int main()
{
	int arr[] = { 2,5,3,1,3,4 };
	int len = sizeof(arr) / sizeof(arr[0]);
	Quick_Sort(arr, len);
	for (int i = 0; i < len; i++)
	{
		printf("%d ",arr[i]);
	}
	return 0;
}

2.非递归代码实现：

#include<stdio.h>
int Partition(int* arr, int left, int right)
{
	int tmp = arr[left];
	while (left<right)
	{
		while (left<right&&tmp <=arr[right])
		{
			right--;
		}
		if (left == right)
		{
			break;
		}
		arr[left] = arr[right];
		while (left<right&&tmp > arr[left])
		{
			left++;
		}
		if (left == right)
		{
			break;
		}
		arr[right] = arr[left];
	}
	arr[left] = tmp;
	return left;
}

#include <stack>
void Quick_No_Recursion(int arr[], int left, int right)
{
    std::stack<int> st;
    st.push(left);
    st.push(right);

    while (!st.empty())
    {
        int tmp_rigiht = st.top();
        st.pop();
        int tmp_left = st.top();
        st.pop();

        int par = Partition(arr, tmp_left, tmp_rigiht);
        if (left < par - 1)
        {
            st.push(left);
            st.push(par - 1);
        }
        if (par + 1 < right)
        {
            st.push(par + 1);
            st.push(right);
        }
    }
}
void Quick_Sort(int* arr, int len)
{
	Quick_No_Recursion(arr, 0, len - 1);
}
int main()
{
	int arr[] = { 2,5,3,1,3,4 };
	int len = sizeof(arr) / sizeof(arr[0]);
	Quick_Sort(arr, len);
	for (int i = 0; i < len; i++)
	{
		printf("%d ",arr[i]);
	}
	return 0;
}