指针交换函数

#include<stdio.h>
void swap1(int x,int y),swap2(int *px,int *py),swap3(int *px,int *py);
int main(){
int a=1,b=2;
int *pa=&a,*pb=&b;

swap1(a,b);
printf("After calling swap1:a=%d b=%d\n",a,b);

a=1;b=2;
swap2(pa,pb);
printf("After calling swap2:a=%d b=%d\n",a,b);

a=1;b=2;
swap3(pa,pb);
printf("After calling swap3:a=%d b=%d\n",a,b);

return 0;
}

void swap1(int x,int y){
int t;
t=x;
x=y;
y=t;
}

void swap2(int *px,int *py){
int t;
t=*px;
*px=*py;
*py=t;
}

void swap3(int *px,int *py){
int *pt;
pt=px;
px=py;
py=pt;
}