题目https://www.luogu.org/problemnew/show/P1449
#include<cstdio>
#include<iostream>
#include<string.h>
#include<stack>
using namespace std;
char a[10000];
int main()
{
int i=0;
stack<double>a;
char ctf;int sum=0;
while(1)
{
int c;int f;
ctf = getchar();
switch(ctf)
{
case '+':c = a.top();a.pop();f=( (a.top())+c );a.pop();a.push(f) ;break;
case '/':c = a.top();a.pop();f=((a.top())/c);a.pop();a.push(f) ;break;
case '*':c = a.top();a.pop();f=( (a.top())* c);a.pop();a.push(f) ;break;
case '@':printf("%.lf\n",a.top());return 0;;
case '-':c = a.top();a.pop();f=((a.top()) - c);a.pop();a.push(f) ;break;
case '.':a.push(sum);sum=0;break;
default:sum = sum * 10 + ctf-'0';break;
}
}
return 0;
}