SPOJ Problem 4452:Simple Arithmetics II

#include<cstdio>
#include<cstring>
char s[20];
int n,i,j,ans,symbol,a,l;
int main(){
    scanf("%d",&n);
    while(n--){
        ans=symbol=0;
        while(scanf("%s",s)&&s[0]!='='){
            if (s[0]>47){
                a=0;
                l=strlen(s);
                for (i=0;i<l;i++)
                    a=a*10+s[i]-48;
                if (symbol==0)ans=a;
                if (symbol==1)ans+=a;
                if (symbol==2)ans-=a;
                if (symbol==3)ans*=a;
                if (symbol==4)ans/=a;
            }
            if (s[0]=='+')symbol=1;
            if (s[0]=='-')symbol=2;
            if (s[0]=='*')symbol=3;
            if (s[0]=='/')symbol=4;
        }
        printf("%d\n",ans);
    }
}

 

模拟，无法理解为何是从左往右算。。