C++关于引用的小知识

#include <iostream>
using namespace std;
void fun1(int b)
{
b = 1;
}
void fun2(int &b)
{
b = 2;
}
void fun3(int *b)
{
*b = 3;
}
void main()
{
int a = 0;
fun1(a);
cout << "调用fun1后，a的值为：" << a << endl;
fun2(a);
cout << "调用fun2后，a的值为：" << a << endl;
fun3(&a);
cout << "调用fun3后，a的值为：" << a << endl;

}

下面3个不同的方法来加注理解

void swap1(int &a,int &b)
{
int t;
t = a;
a = b;
b = t;
}
int main()
{
int x = 5;
int y = 10;
cout << x << " " << y << endl;
swap1(x, y);
cout << x << " " << y << endl;// 结果是10，5
return 0;
}

void swap1(int a,int b)
{
int t;
t = a;
a = b;
b = t;
}
int main()
{
int x = 5;
int y = 10;
cout << x << " " << y << endl;
swap1(x, y);
cout << x << " " << y << endl;// 结果是5，10，不是 引用，x和y的值压根就没有变化
return 0;
}

void swap1(int &a,int b)
{
int t;
t = a;
a = b;
b = t;
}
int main()
{
int x = 5;
int y = 10;
cout << x << " " << y << endl;
swap1(x, y);
cout << x << " " << y << endl;// 10，10
return 0;
}