dequeue imple

//Initial Template for C++

// CPP code to implement dequeue functions
#include <bits/stdc++.h>
using namespace std;


 // } Driver Code Ends


//User function Template for C++

/* Function to push element to front
* dq : dqueue in which element is to be pushed
* x : element to be pushed
*/
void push_back_pb(deque<int> &dq, int x){

    // Your code here
    dq.push_back(x);

}

/* Function to pop element from back
* dq : dqueue From which element is to be popped
*/
void pop_back_ppb(deque<int> &dq){

    if(!dq.empty()) dq.pop_back();


}

/* Function to return element from front
* dq : dqueue from which element is to be returned
*/
int front_dq(deque<int> &dq){

if(!dq.empty()) return dq.front();
    /*Your code here*/
    else
    return -1;

}

/* Function to push element to front
* dq : dqueue in which element is to be pushed
* x : element to be pushed
*/
void push_front_pf(deque<int> &dq, int x){

    // Your code here
    dq.push_front(x);

}

// { Driver Code Starts.

// Driver code
int main() {

    int testcase;
    cin >> testcase;

    // declaring deque
    deque<int> dq;

    while(testcase--){

        int queries;
        cin >> queries;

        while(queries--){
        string s;
        cin >> s;

        // if query is to push back
        if(s == "pb"){
            int x;
            cin >> x;
            push_back_pb(dq, x);
            cout << dq.back() << endl;
        }

        // if query is to push front
        if(s == "pf"){
            int x;
            cin >> x;
            push_front_pf(dq, x);
            cout << dq.front() << endl;
        }

        // if query is to pop back
        if(s == "pp_b"){
            pop_back_ppb(dq);
            cout << dq.size() << endl;
        }

        // if query is to return front
        if(s == "f"){
            int x = front_dq(dq);
            cout << x << endl;
        }
        }
        dq.clear();
    }

    return 0;
}  // } Driver Code Ends