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

#define WEIGHT 3.0e-23
#define KQ     950

static void water(void)
{
    float num;
    float sum;

    printf("Please input for num:");
    scanf("%f", &num);

    if (num <= 0)
    {
        fprintf(stderr, "Input Error!\n");
        exit(1);
    }
    sum = num * KQ / WEIGHT;

    printf("Total = %e\n", sum);

    return;
}

static void area(void)
{
    float a, b, c;
    float s, area;

    printf("Please input:");
    scanf("%f%f%f", &a, &b, &c);
    // 对scanf做好校验是好习惯
    if (a + b <= c || b + c <= a || a + c <= b)
    {
        fprintf(stderr, "EINVAL!\n");
        exit(0);
    }

    printf("a = %f\n", a);
    printf("b = %f\n", b);
    printf("c = %f\n", c);

    // s = 1 / 2 * (a + b + c);
    s = 1.0 / 2 * (a + b + c);
    printf("s = %f\n", s);
    // s=0.000000
    // 1 / 2是int型计算，得到的是商0余1

    area = sqrt(s * (s - a) * (s - b) * (s - c));
    printf("area = %f\n", area);
}

void root(void)
{
    float a, b, c;
    float disc;
    float p, q;
    float x1, x2;

    printf("Please input :\n");
    scanf("%f%f%f", &a, &b, &c);

    if (b * b - 4 * a * c < 0)
    {
        fprintf(stderr, "EINVAL\n");
        exit(1);
    }
    disc = b * b - 4 * a * c;
    p    = -b / 2 * a;
    q    = sqrt(disc) / 2 * a;

    x1 = p + q;
    x2 = p - q;

    printf("x1 = %f\n", x1);
    printf("x2 = %f\n", x2);
}

int main( )
{
    // water();

    // area();

    root( );

    exit(0);
}