c++中用指针交换两个变量的值

#include <iostream.h>

void change(int* x,int* y)
{
 int temp;

 temp = *x;
 *x = *y;
 *y = temp;

 return;
}

int main_all()
{
 int a,b;
 int *p_a,*p_b; 
 a = 1;
 b = 2;
 
 p_a = &a;
 p_b = &b;

 change(p_a,p_b);
 
 cout<<"a = "<<a<<" and b = "<<b<<endl;
 return(0);
}