注意：是传送地址，才能改变原数据！！！

#include<stdio.h>
void swap(int* pa, int* pb)
{
  int z = 0;
  z = *pa;
  *pa = *pb;
  *pb = z;
  return 0;
}
int main()
{
  int a = 210;
  int b = 320;
  printf("%d %d\n", a, b);
  swap(&a,&b);
  printf("%d %d", a, b);

  return 0;
}