1028: C语言程序设计教程（第三版）课后习题8.2

题目描述

求方程 的根，用三个函数分别求当b^2-4ac大于0、等于0、和小于0时的根，并输出结果。从主函数输入a、b、c的值。

输入

a b c

输出

x1=? x2=?

样例输入

4 1 1

样例输出

x1=-0.125+0.484i x2=-0.125-0.484i

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

// delta = 0
void delta_eq_0(int a, int b, int c)
{
    float res = (float)(0 - b) / (2 * a);
    printf("x1=%.3f x2=%.3f
", res, res);
}

// delta > 0
void delta_gt_0(int a, int b, int c)
{
    int delta = b * b - 4 * a * c;
    float res1, res2;
    res1 = (-b+sqrt(delta)) / (2 * a);
    res2 = (-b-sqrt(delta)) / (2 * a);
    printf("x1=%.3f x2=%.3f
", res1, res2);
}

// delta < 0
void delta_lt_0(int a, int b, int c)
{
    int delta = b * b - 4 * a * c;
    float res1, res2;
    res1 = (float)(0 - b) / (2 * a);
    res2 = sqrt(abs(delta)) / (2 * a);
    printf("x1=%.3f+%.3fi x2=%.3f-%.3fi
", res1, res2, res1, res2);
}

// 计算结果
void caculate(int a, int b, int c)
{
    int delta = b * b - 4 * a * c;
    
    if(delta == 0)    
        delta_eq_0(a, b, c);
    else if(delta > 0)
        delta_gt_0(a, b, c);
    else        
        delta_lt_0(a, b, c);
}


int main(int argc, char const *argv[])
{

    int a, b, c;
    scanf("%d%d%d", &a, &b, &c);
    caculate(a, b, c);
    return 0;
}