#include<stdio.h>
main()
{
int x,z;
float y;
scanf("%d",&x);
z=(int)(x/10);
switch(z)
{
case 0: y = x; printf("y=x=%d\n",y);break;
case 1: y = 10; printf("y = %d\n",y);break;
case 2: y=(-0.5)*x+20; printf("y=-0.5*x+20=%f\n",y);break;
default: printf("你输入的有问题\n");break;
}
}
不知道你是不是这个意思。