例题：a=5,b=3.输出a=3,b=5
void w(int a,int b)
{
int t=0;
t=a;a=b;b=t;
}
int main()
{
int a=5,b=3;
int pa=0;
int pb=0;
pa=&a;
pb=&b;
w(pa,pb);
printf("a=%d,b=%d",a,b);
return 0;
}