第四章（2）

例4.7

#include<stdio.h>
int main()
{
void action1(int,int),action2(int,int);
char ch;
int a=15,b=23;
ch=getchar();
switch(ch)
{
case 'a' :
case'A' : action1(a,b);break;
case'b' :
case'B' : action2(a,b);break;
.
.
.
default：putchar('\a');
}
return 0;
}
void action1(intx,inty)
{
printf("x+y=%d\n",x+y);
}
void action2(intx,inty)
{
printf("x*y=%d\n",x*y);
}

运行结果如下

例4.8

#include<stdio.h>
int main()
{
int a;
scanf("%d",&a);
if(x%4==0 && x%100==0 || x%400!=0)
printf("%d是闰年\n",x);
else
printf("%d不是闰年\n",x);
return 0;
}

运行结果如下

例4.9

# include <stdio.h>
# include <math.h>
int main()
{
	double a,b,c,disc,realpart,imagpart,x1,x2;
	scanf("%lf%lf%lf",&a,&b,&c);
	if(a==0)
		printf("该方程不是二次方程");
	else
	{	disc=b*b-4*a*c;
	if(disc==0)
		printf("has two eaual roots:%8.4f\n",-b/(2*a));
	else
	{	if(disc<0)
	{realpart=-b/(2*a);
	imagpart=sqrt(-disc)/(2*a);
	printf("has comples roots:\n");
	printf("%8.4f+%8.4fi\n",realpart);
	printf("%8.4f-%8.4fi\n",imagpart);}
	     else
		 {	x1=(-b+sqrt(disc))/(2*a);
		 x2=(-b-sqrt(disc))/(2*a);
		 printf("has distinct real roots:%8.4f and %8.4f\n",x1,x2);}
	}
	}
	return 0; 
}

运行结果如下：

例4.10

# include <stdio.h>
int main()
{
	int c,s;
	float p,w,d,f;
	printf("please enter price,weight,discount:");
	scanf("%f%f%d",&p,&w,&s);
	if(s>=3000)c=12;
	else c=s/250;
	switch(c)
	{
	case 0:d=0;break;
	case 1:d=2;break;
	case 2:
	case 3:d=5;break;
	case 4:
	case 5:
	case 6:
	case 7:d=8;break;
	case 8:
	case 9:
	case 10:
	case 11:d=10;break;
	case 12:d=15;break;
	}
	f=p*w*s*(1-d/100);
	printf("freight=%10.2f\n",f);
	return 0;
}

运行结果如下：