题解 | #计算一元二次方程#

#include <stdio.h>
#include <math.h>

int main()
{
    double a = 0.0;
    double b = 0.0;
    double c = 0.0;

    //多组输入
    while (~scanf(" %lf%lf%lf", &a, &b, &c))
    {
        if (0.0 == a)
        {
            //不是一元二次方程
            printf("Not quadratic equation\n");
        }
        else
        {
            //是一元二次方程
            //一元二次方程判别式
            double disc = b * b - 4 * a * c;
            if (0.0 == disc)
            {
                //两实根相等
                printf("x1=x2=%.2lf\n", -b / (2 * a));
            }
            else if (disc > 0.0)
            {
                //两实根不等
                printf("x1=%.2lf;x2=%.2lf\n", (-b - sqrt(disc)) / (2 * a), (-b + sqrt(disc)) / (2 * a));
            }
            else
            {
                //有两个虚根
                printf("x1=%.2lf-%.2lfi;x2=%.2lf+%.2lfi\n", -b / (2 * a), sqrt(-disc) / (2 * a), -b / (2 * a), sqrt(-disc) / (2 * a));
            }
        }
    }

    return 0;
}