排序——快速排序（三数取中法和优化不必要交换）

#include <iostream>
#include <stdlib.h>
using namespace std;

#define MAXSIZE 10

void swap(int k[], int low,int high)
{
int temp;

temp = k[low];
k[low] = k[high];
k[high] = temp;
}

int Partition(int k[], int low, int high)
{
int point;

int m = low + (high - low)/2;

if(k[low] > k[high])
{
swap(k, low ,high);
}
if(k[m] > k[high])
{
swap(k, m ,high);
}
if(k[m] > k[low]) // 使得low存放中间的值
{
swap(k, m, low);
}

point = k[low];

while(low < high)
{
while( low < high && k[high] >= point ) //过滤掉比low大的
{
high--;
}//出了循环说明要进行移动
k[low] = k[high];

while( low < high && k[low] <= point )
{
low++;
} //出了循环说明左边大于右边 要进行移动
k[high] = k[low];

}

k[low] = point;

return low;
}

void QSort(int k[], int low, int high)
{
int point;

if( low < high )
{
point = Partition(k , low , high);

QSort(k, low,point-1); //左边

QSort(k, point+1, high); // 右边

}
}

void QuickSort( int k[], int n )
{
QSort( k, 0, n-1 );
}

int main()
{
int i ,a[10] = {5,2,6,0,3,9,1,7,4,8};

QuickSort(a,10);

for( i=0; i < 10 ;i++ )
{
cout << a[i];
}

cout << endl;

return 0;
}