题解 | #计算一元二次方程#

#include <iostream>
#include<iomanip>
#include<cmath>
using namespace std;

int main()
{
	float a = 0;		//定义a,b,c
	float b = 0;
	float c = 0;

	while (cin >> a >> b >> c) {	//多组输入
		if (a == 0) {		//判断a是否为0
			cout << "Not quadratic equation" << endl;
		}
		else {
			float delta = b * b - 4 * a * c;
			if (delta == 0) {
				float x;
				if (b == 0 && a > 0) {
					x = b / (2 * a);
				}
				else {
					x = (-b) / (2 * a);
				}
				cout << fixed << setprecision(2) << "x1=x2=" << x << endl;
			}
			else if (delta > 0) {
				float x1 = ((-b) - sqrt(delta)) / (2 * a);
				float x2 = ((-b) + sqrt(delta)) / (2 * a);
				cout << fixed << setprecision(2) << "x1=" << x1 << ";" << "x2=" << x2 << endl;
			}
			else if (delta < 0) {
				float shi = (-b) / (2 * a);
				float xu = sqrt(-delta) / (2 * a);
				if (a > 0) {
					cout << fixed << setprecision(2) << "x1=" << shi << "-" << xu
						<< "i;x2=" << shi << "+" << xu << "i" << endl;
				}
				else if (a < 0) {
					cout << fixed << setprecision(2) << "x1=" << shi << "+" << xu
						<< "i;x2=" << shi << "-" << xu << "i" << endl;
				}
			}
		}
	}

	return 0;

}