队列练习2

Posted 2020-06-24

#include<cstdio>
#include<iostream>
#include<queue>
using namespace std;
int n,k,a,t=1;
int main()
{
    queue<int>line;
    cin>>n;
    while(n--)
    {
        cin>>k;
        if(k==1)
        {
            cin>>a;
            line.push(a);
        }
        if(k==2)
        {
            if(line.empty())  
            {
                //cout<<"impossible!"<<endl;
                //return 0;
                t=0; 
                continue;
            }
            line.pop();
        }
    }
    if(line.empty()||t==0)  cout<<"impossible!"<<endl;
   else cout<<line.front()<<endl;
    return 0;    
}