1058：求一元二次方程-信息学奥赛一本通

#include<algorithm>

#include<cmath>

#include<cstdio>

#include<iostream>

using namespace std;

int main(){

double a,b,c,x1,x2,delta,zero=0.000001;

cin>>a>>b>>c;

delta=b*b-4*a*c;

// delta<0

if(delta<-zero){

cout<<"No answer!";

}

//-0.000001 <= delta <= 0.000001

else if(fabs(delta)<=zero){

x1=-b/(2*a);

printf("x1=x2=%.5lf",x1);

}

else{

x1=(-b+sqrt(delta))/(2*a);

x2=(-b-sqrt(delta))/(2*a);

if(x1<x2){

printf("x1=%.5lf;x2=%.5lf",x1,x2);

}

else{

printf("x1=%.5lf;x2=%.5lf",x2,x1);

}

}

return 0;

}