解一元二次方程式

//
//  main.cpp
//  Codehomework#2 Solving quadratic equation
//
//  Created by YTC on 2022/3/9.
//
#include <iostream>
#include <cmath>

using namespace std;


int main() {
    double a,b,c,x1,x2,realpart,imaginarypart;
    
    cout<<">>請輸入一元二次程式之係數 a, b, 和 c:"<<endl;
   
    cin >> a >> b >> c;
    double discriminant = b*b-4*a*c; //discriminant 為判別式
    
        cout<<"您所輸入之一元二次方程式如下：\n";
        cout<<a<<"x^2"<<"+"<<b<<"x"<<"+"<<c<<" = 0"<<endl;
        
        if(a == 0){
            if(b == 0)
            {
                if(c == 0)
                {
                    cout<<"全部都0是在打心酸的？？"<<endl;
                }
                else{
                    cout<<"ERROR occur"<<endl;
                }
            }
            
            else{
                if(c == 0){  //(a, b, c) = (0, 1, 0)
                    x1 = c/b;
                    cout<<"有一根："<< x1 <<endl;
                    
                }
                else {
                    x1 = -c/b; // bx = -c
                    cout<<"有一根："<< x1 <<endl;
                }
                }
            }
         
        else{
        
            if(discriminant>0)
        {
            x1 = (-b+sqrt(discriminant))/2*a;
            x2 = (-b-sqrt(discriminant))/2*a;
            cout<<"有兩相異實根："<<x1<<","<<x2<<endl;
        }
        
            else if(discriminant == 0)
        {
            x1 = -b/2*a;
            cout<<"有兩相同實根："<< x1 <<"," << x1 <<endl;
        }
            
            else if(discriminant < 0)
        {
            realpart = -b/2*a;
            imaginarypart = sqrt(abs(discriminant))/2*a;
            cout<<"有兩虛根（或無實根）："<<realpart<<'+'<<imaginarypart<<"i"<<","<< realpart << -imaginarypart << "i"<<endl;
        }
    }
    char again;
    cout<<"是否要繼續？（y/n)"<<endl;
    cin >> again;
    if(again == 'y' || again =='Y'){
        return main();
    }
    else if(again == 'n' || again == 'N'){
        return 0;
    }
      }