第十二周阅读程序（1）

#include <iostream>using namespace std;class Sample{private:    int x;public:    Sample () { }   //1    Sample(int a){x=a;}   // 2    void disp(){cout<<"x="<<x<<endl;}   //3     friend Sample operator+( Sample &s1, Sample &s2);};Sample operator+( Sample &s1, Sample &s2)    //4{    return Sample(s1.x+s2.x);}int main(){    Sample obj1(10);    Sample obj2(20);    Sample obj3;    obj3=obj1+obj2;    obj3.disp();    return 0;}