// 計算兩個複數之積 
#include <stdio.h>
#include <math.h>

struct Complex {
	double real;
	double imag;
};

void Multiply(struct Complex *p, struct Complex c1, struct Complex c2);

void Show(struct Complex c);

int main(void)
{
	struct Complex c1,c2,c3;
	printf("請輸入第一個複數的實部和虛部: ");
	scanf("%lf%lf",&c1.real,&c1.imag);
	printf("請輸入第二個複數的實部和虛部: ");
	scanf("%lf%lf",&c2.real,&c2.imag);
	
	Multiply(&c3,c1,c2);	//複數相乘 
	
	Show(c3);				//顯示結果 
	
	return 0;
}

void Multiply(struct Complex *p, struct Complex c1, struct Complex c2)
{
	p->real = c1.real*c2.real-c1.imag*c2.imag;
	p->imag = c1.real*c2.imag+c1.imag*c2.real;
}

void Show(struct Complex c)
{	
	// 實部和虛部均為0 
	if (fabs(c.real)<1e-4&&fabs(c.imag)<1e-4)
	{
		printf("兩數相乘結果為: 0\n");
	}
	// 實部為0,虛部不為0 
	else if (fabs(c.real)<1e-4)
	{
		printf("兩數相乘結果為: %fi\n",c.imag);
	}
	// 實部不為0,虛部為0
	else if (fabs(c.imag)<1e-4)
	{
		printf("兩數相乘結果為: %f\n",c.real);
	} 
	// 實部不為0,虛部大於0 
	else if (c.imag>0)
	{
		printf("兩數相乘結果為: %f+%fi\n",c.real,c.imag);
	} 
	// 實部不為0,虛部小於0
	else 
	{
		printf("兩數相乘結果為: %f%fi\n",c.real,c.imag);
	}
}