2771 - 复数类（运算符重载）
定义一个复数类Complex，重载运算符"","<<",">>"，使之能够用于复数的乘法、输入、输出。复数乘法公式(a+bi)(c+di)=(ac-bd)+(bc+ad)i.主函数定义如下：
int main()
{Complex c1,c2,c3;
cin>>c1>>c2;
c3=c1c2;
cout<<c3;
return 0;}
Input
每行二个整数，表示复数的实部和虚部。输入二个复数，必须用cin>>c1>>c2;
Output
输出一个复数，输出时不要换行，必须用cout<<c3;
Examples
Input
2 3 4 5
Output
-7+22i
Solution C++
#include <iostream> using namespace std; class Complex { int real,imag; public: Complex( ):real(0),imag(0){} Complex(int r,int i):real(r),imag(i){} friend Complex operator *(Complex& c1,Complex& c2); friend istream & operator>>(istream & input,Complex& c); friend ostream & operator<<(ostream & out,Complex& c); }; istream & operator>>(istream &input,Complex& c) {input>>c.real>>c.imag; return input;} ostream & operator<<(ostream & out,Complex& c) { out<<c.real; if (c.imag>0) out<<"+"; if (c.imag!=0) out<<c.imag<<"i"<<endl; return out;} Complex operator *(Complex& c1,Complex& c2) {Complex c; c.real=c1.real*c2.real-c1.imag*c2.imag; c.imag=c1.imag*c2.real+c1.real*c2.imag; return c; } int main() {Complex c1,c2,c3; cin>>c1>>c2; c3=c1*c2; cout<<c3; return 0;}