第五阶段—函数—函数的传参—地址传递：要求在swap函数中让 a和b值的交换。

#include<stdio.h>
void swap(int *x, int *y)
{
    int temp = 0;
    temp = *x;
    *x = *y;
    *y = temp;
    return;
}

int main(int argc, const char *argv[])
{
    int a = 0, b = 0;//定义需要传给形参，给形参赋值的变量
    printf("plese input two number:");
    scanf("%d%d",&a,&b);
    printf("a = %d,b = %d\n",a , b);
    swap(&a, &b);
    
    printf("a = %d,b = %d\n",a , b);    
    return 0;
}