题解 | #加减乘除#

#include<stdio.h>
#include<string.h>
int main()
{
    char S[100],op='0';
    gets(S);
    int flag=0,i,n=strlen(S),num1,num2=1,ans;
    for(i=0;i<n;i++)
    {
        if(S[i]=='!')flag=1;
    }
    if(flag==1)
    {
        sscanf(S,"%d %*c",&num1);
        for(ans=1,i=1;i<=num1;i++)
        {
                ans*=i;
        }
    }
    else if(flag==0)
    {

        sscanf(S,"%d %c %d",&num1,&op,&num2);
        switch(op)
        {
            case '+':ans=num1+num2;
            break;
            case '-':ans=num1-num2;
            break;
            case '*':ans=num1*num2;
            break;
            default:if(num2==0){
                printf("error");break;
            }
            else if(op=='/')ans=num1/num2;
            else if(op=='%')ans=num1%num2;
            break;
        }
    }
    if(!(num2==0&&(op=='%'||op=='/')))printf("%d\n",ans);
    return 0;
}