测试点

#include<bits/stdc++.h>
#define aa !a[dq].empty()
using namespace std;
typedef long long ll;
ll q,dq,x;
deque<ll>a[100005];
string use;
const string s="push_back",s1="pop_back",s2="push_front",s3="pop_front",s4="size",s5="front",s6="back";
signed main(){
	cin>>q;
	while(q--){
		cin>>use>>dq;
		if(use==s){
			cin>>x;
			a[dq].push_back(x);
		}
		else if(use==s1&&aa)a[dq].pop_back();
		else if(use==s2){
			cin>>x;
			a[dq].push_front(x);
		}
		else if(use==s3&&aa)a[dq].pop_front();
		else if(use==s4&&aa)cout<<a[dq].size()<<endl;
		else if(use==s5&&aa)cout<<a[dq].front()<<endl;
		else if(use==s6&&aa)cout<<a[dq].back()<<endl;
	}
	return 0;
}