关于一个快速排序的C++问题

#include<iostream.h>
void qsort(int a[],int left,int right);
void main()
{
int a[9]={8,3,9,7,25,100,26,39,2 },len,i;
len=sizeof(a)/sizeof(int);
cout<<"排序前："<<endl<<'\n';
for(i=0;i<len;i++)
cout<<a[i]<<",";
cout<<'\b'<<' '<<endl<<endl<<endl;
qsort(a,0,len-1);
cout<<"排序后： "<<endl<<endl;
for(i=0;i<9;i++)
cout<<a[i]<<",";
cout<<'\b'<<" ";
cin.get();

}

void qsort(int a[],int left,int right)
{
int l,r,midpoint,temp;
l=left;
r=right;
midpoint=a[(left+right)/2];
while(l<r)
{
while(a[l]>midpoint) ++l;
while(a[r]<midpoint) --r;
if(r==l) break;
temp=a[l];
a[l]=a[r];
a[r]=temp;
++l;