函数参数传递_使用引用避免拷贝

int test_demo(int *p)
{
    *p = 5;
    return 0;//改变指向，未改变地址
}
int main(int argc,char *argv[])//main函数
{
    int a= 1;
    int* p = &a;
    cout << &a << endl;
    test_demo(&a);
    cout << &a << endl;
    cout << a << endl;
    system("pause");//stop
 }

int test_demo(int &p)
{
    int a = 5;
    p = a;
    return 0;
}
int main(int argc,char *argv[])//main函数
{
    int a= 1;
    int* p = &a;
    cout << &a << endl;
    test_demo(a);
    cout << &a << endl;
    cout << a << endl;
    system("pause");//stop
 }