题解 | #计算一元二次方程#

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

int main() {
    float a, b, c, d, x1, x2, m, n;
    while (~scanf("%f%f%f", &a, &b, &c)) {
        d = b * b - 4 * a * c;
        if (a == 0) {
            printf("Not quadratic equation\n");
        } else if (d == 0) {
            x1 = x2 = -b / (2 * a);
            if (fabs(x1) < 1e-6) {
                printf("x1=x2=0.00\n");
            } else {
                printf("x1=x2=%.2f\n", x1);
            }
        } else if (d > 0) {
            x1 = (-b - sqrt(d)) / (2 * a);
            x2 = (-b + sqrt(d)) / (2 * a);
            if (fabs(x1) < 1e-6) {
                printf("x1=0.00;");
            } else {
                printf("x1=%.2f;", x1);
            }
            if (fabs(x2) < 1e-6) {
                printf("x2=0.00\n");
            } else {
                printf("x2=%.2f\n", x2);
            }
        } else {
            m = -b / (2 * a);
            n = sqrt(-d) / (2 * a);
            if (n > 0) {
                printf("x1=%.2f-%.2fi;x2=%.2f+%.2fi\n", m, n, m, n);
            } else if (n < 0) {
                printf("x1=%.2f+%.2fi;x2=%.2f-%.2fi\n", m, -n, m, -n);
            } else {
                if (fabs(m) < 1e-6) {
                    printf("x1=x2=0.00\n");
                } else {
                    printf("x1=x2=%.2f\n", m);
                }
            }
        }
    }
    return 0;
}