题解 | #二次方程计算器#

#include<iostream>
#include<iomanip>
using namespace std;
#include<algorithm>
#include<math.h>
#include<string>
void f(double a1, double a2, double b1, double b2,double  c1, double c2) {
	double A = a1 - a2;
	double B = b1 - b2;
	double C = c1 - c2;
	double delt = B * B - 4 * A*C;
	if (delt >= 0) {
		double x1, x2;
		x1 = (-B - sqrt(delt)) / (2 * A);
		x2 = (-B + sqrt(delt)) / (2 * A);
		if (x1 <= x2) {
			cout << fixed << setprecision(2) << x1 << " " << x2 << endl;
		}
		else {
			cout << fixed << setprecision(2) << x2 << " " << x1 << endl;
		}
		
	}
	else {
		cout << "No Solution" << endl;
	}
}
void f2(double &a1, double &b1,double  &c1, string s1) {

	//二次项
	if (s1.find("x^2", 0) != s1.npos) {
		int i = s1.find("x^2", 0)-1;
		for (; i >= 0; i--) {
			if ((s1[i]<'0' || s1[i]>'9') && s1[i] != '-')break;
		}
		if (i == s1.find("x^2", 0) - 1) {//系数为1
			a1 = 1;
			s1.erase(i + 1, s1.find("x^2", 0) + 2 - i);
		}
		else {
			string str1 = s1.substr(i + 1, s1.find("x^2", 0) - i-1);
			s1.erase(i + 1, s1.find("x^2", 0) + 2 - i);
			a1 = stoi(str1);
		}
		
	}
	//一次
	if (s1.find("x", 0) != s1.npos) {
		int  i = s1.find("x", 0) - 1;
		for (; i >= 0; i--) {
			if ((s1[i]<'0' || s1[i]>'9')&&s1[i]!='-')break;
		}
		if (i == s1.find("x", 0) - 1) {
			b1 = 1;
			s1.erase(i + 1, s1.find("x", 0) - i);
		}
		else {
			string str2 = s1.substr(i + 1, s1.find("x", 0) -i- 1);
			s1.erase(i + 1, s1.find("x", 0) - i);
			b1 = stoi(str2);
		}
		
	}
	//常数
	while (s1.find('+', 0) != s1.npos) {
		s1.erase(s1.find('+', 0), 1);
	}
	if (s1.size() != 0) {
		//cout << "s1="<<s1 << endl;
		c1 = stoi(s1);
	}
}
int main() {
	ios::sync_with_stdio(false);

	string s;
	while (cin >> s) {
		string s1, s2;
		s1 = s.substr(0, s.find('=', 0));
		s2 = s.substr(s.find('=', 0) + 1, s.size() - s.find('=', 0) - 1);
		//cout << s1 << endl << s2 << endl;

		double a1 = 0, a2 = 0, b1 = 0, b2 = 0, c1 = 0, c2 = 0;

		f2(a1, b1, c1, s1);
		//cout << a1 << "," << b1 << "," << c1 << endl;
		f2(a2, b2, c2, s2);



		f(a1, a2, b1, b2, c1, c2);
	}
	return 0;
}