题解 | 计算一元二次方程

#include <stdio.h>
#include <math.h>
int main(void)
{
    double a, b, c, d, x1, x2, t, i, n;
    while (scanf("%lf %lf %lf", &a, &b, &c) != EOF)
    {
        d = (b * b) - (4 * a * c);
        x1 = (-b + sqrt(d)) / (2 * a);
        x2 = (-b - sqrt(d)) / (2 * a);
        i = sqrt(-d) / (2 * a);
        n = -b / (2 * a);
        if (n == -0.0)
            n = fabs(n);
        if (x1 == -0.0)
            x1 = fabs(x1);
        if (x2 == -0.0)
            x2 = fabs(x2);
        if (a == 0)
            printf("Not quadratic equation\n");
        else if (d == 0)
            printf("x1=x2=%.2lf\n", x1);
        else if (d > 0)
        {
            if (x1 > x2)
            {
                t = x1;
                x1 = x2;
                x2 = t;
            }
            printf("x1=%.2lf;x2=%.2lf\n", x1, x2);
        }
        else if (d < 0)
            printf("x1=%.2lf-%.2lfi;x2=%.2lf+%.2lfi\n", n, i, n, i);
    }
}