w3-4 后缀表达式

#include <iostream>
#include <stack>
using namespace std;
long long tmp1,tmp2,tmp3;
int main() {
    stack<long long>a;
    char ch;
    cin>>ch;
    while(ch!='@'){//到@停止
        if(ch>='0'&&ch<='9'){//当输入数字字符时
            tmp1=ch-'0';
            cin>>ch;
            while(ch>='0'&&ch<='9'){//用tmp1记录该数字
                tmp1*=10;
                tmp1+=ch-'0';
                cin>>ch;
            }
            a.push(tmp1);//进栈
        }
        if(ch=='+'){
            tmp2=0;
            tmp2+=a.top();
            a.pop();
            tmp2+=a.top();
            a.pop();
            a.push(tmp2);
        }
        else if(ch=='-'){
            tmp2=0;
            tmp2-=a.top();
            a.pop();
            tmp2+=a.top();
            a.pop();
            a.push(tmp2);
        }
        else if(ch=='*'){
            tmp2=0;
            tmp2+=a.top();
            a.pop();
            tmp2*=a.top();
            a.pop();
            a.push(tmp2);
        }
        else if(ch=='/'){
            tmp2=0;
            tmp3=a.top();
            a.pop();
            tmp2+=a.top();

            a.pop();
            a.push(tmp2/tmp3);
        }
        cin>>ch;
    }
    cout<<a.top();
    return 0;
}