快速排序

# include <stdio.h>


int FindPos(int * a, int low, int high);
void QuickSort(int * a, int low, int high);


int main(void)
{
int a[6] = {-2, 1, 0, -985, 4, -93};
int i;


QuickSort(a, 0, 5); //第二个参数表示第一个元素的下标  第三个参数表示最后一个元素的下标

for (i=0; i<6; ++i)
printf("%d  ", a[i]);
printf("\n");


return 0;
}


void QuickSort(int * a, int low, int high)
{
int pos;


if (low < high)
{
pos = FindPos(a, low, high);
QuickSort(a, low, pos-1);
QuickSort(a, pos+1, high);
} 
}


int FindPos(int * a, int low, int high)
{
int val = a[low];


while (low < high)
{
while (low<high  && a[high]>=val)
--high;
a[low] = a[high];


while (low<high && a[low]<=val)
++low;
a[high] = a[low];
}//终止while循环之后low和high一定是相等的


a[low] = val; 


return high; //high可以改为low, 但不能改为val 也不能改为a[low]  也不能改为a[high]
}