队列简单解法

解题思路:

注意事项:

参考代码:

#include <iostream>

#include <queue>

using namespace std;

int main(){

queue<int> st;

int n,i,x,y;

cin>>n;

for(i=1;i<=n;i++){

cin>>x;

switch(x){

case 1:

cin>>y;

st.push(y);

break;

case 2:

if(!st.empty()){

cout<<st.front()<<endl;

st.pop();

}else{

cout<<"no"<<endl;

return 0;

}

break;

case 3:

cout<<st.size()<<endl;

break;

}

}

return 0;

}