#include<stdio.h>
int main()
{
    int a,b,result;
    char ope;                        //operator：运算符
    printf("请输入数字和运算符：");
    scanf("%d%c%d",&a,&ope,&b);
    switch(ope)
    {   
        case '+':result = a + b;break;
        case '-':result = a - b;break;
        case '*':result = a * b;break;
        case '/':result = a / b;break;
        case '%':result = a % b;break;
        default :printf("illegal operator\n");
    }
    printf("%d",result);
    return 0;
}
错误：比如输入3+2 结果是 illegal operator。如果输入 3 43 2 结果是5！关键是算术运算符如何被计算机识别！