题解 | #计算一元二次方程#

#include <stdio.h>
#include <math.h>
int main() 
{
	double a,b,c,del;
	while(scanf("%lf%lf%lf",&a,&b,&c)!=EOF)
	{
		if(a==0)
		printf("Not quadratic equation");
		else
		{
			del=b*b-4*a*c;
			if(del==0)
			{

			    float mp = -b + sqrt(del);
			    if(mp == 0)
				{
			        printf("x1=x2=%.2f\n",mp);
			    }else
				{
			        printf("x1=x2=%.2f\n",(-b+sqrt(del))/2.0/a);
			    }
			}
			else if(del>0)
			{
				printf("x1=%.2lf;x2=%.2lf\n",(-b-sqrt(del))/2/a,(-b+sqrt(del))/2/a);
			}
			else
			{
				printf("x1=%.2lf-%.2lfi;x2=%.2lf+%.2lfi\n",-b/2/a,sqrt(-del)/2/a,-b/2/a,sqrt(-del)/2/a);
			}
		}
	}
	return 0;
}

当delta=0时为了防止屏幕输出x1=x2=0.00（原因在-b的－号上），应该对b进行分类讨论