C++ 编程题练习-输出指定结果一（10-2）

C++ 编程题练习-输出指定结果一

来源：coursera c++ pku 期末编程试题

一、题目

填写代码，使输出结果为

2
2
8
10

#include <iostream>using namespace std;class Number {public:    int num;    Number(int n): num(n) {    }// 在此处补充你的代码};int main() {    Number a(2);    Number b = a;    cout << a.value() << endl;    cout << b.value() << endl;    a.value() = 8;    cout << a.value() << endl;    a+b;    cout << a.value() << endl;    return 0;}

二、程序

    Number(const Number & n) { num = n.num; }    Number & value() { return *this; }    friend ostream & operator<<(ostream & os, const Number & n);    friend void operator+(const Number &n1, const Number & n2);

ostream & operator<<(ostream & os, const Number & n){    os<<n.num;    return os;}void operator+(Number &n1, Number & n2){    n1.num += n2.num;}