Ytdyklly

Using feedback from my previous implementation I'm writing a very simple Queue of struct Nodes with only these methods get_front(), get_back(), pop_front(), push_back(), and a ostream friend method. I want this to be reviewed as production code and is to be treated as code that could be used in an interview. I'm really curious about the approach I've taken here to keep track of the size, empty status, and back and front pointers. I resolved some of the padding issues in my data structures, not sure if that's over kill or would look good to show my C++ proficiency.

I'd like to know also if my member functions for the Queue have any edge cases I am not catching and any improvements I can make to run time efficiency overall. Anyway I can simplify this code further with c++11 features, shorter variable names or smart pointers would be appreciated.

Lastly if you optionally would like to share the memory/space complexity for my code that would be a huge help! I have noted some examples in the member data of my Node struct.

#include <iostream>

#include <string>



class Queue

{

    private:

        struct Node

        {

            int data;

            char padding[4];

            Node* previous;

            Node(int data) : data(data), previous(nullptr) { }

        };

        int _size{0};

        char padding[4];

        Node* _back{nullptr};

        Node* _front{nullptr};

    public:

        ~Queue() {

            while(_front) {

                auto n = _front;

                _front = _front->previous;

                delete n;

            }

        }



        void pop_front() {

            --_size;

            if (!_back) {

                throw std::out_of_range{"cannot get data from empty queue"};

            }

            else if (_front->previous) {

                auto danglingptr = _front;

                _front = _front->previous;

                delete danglingptr;

            }

            else {

                _front = _back = nullptr;

            }

        }

        void push_back(int data) {

            auto n = new Node(data);

            ++_size;

            if (!_back) {

                _front = _back = n;

            }

            else {

                _back->previous = n;

                _back = _back->previous;

            }

        }

        int get_back() { return _back ? _back->data : 0; }

        int get_front() { return _front ? _front->data : 0; }

        std::size_t get_size() { return _size; }

        bool is_empty() { return _size > 0; }



        friend std::ostream& operator<<(std::ostream& os, const Queue& queue) {

            int size = queue._size;

            if (size == 0) {

                os << "Queue is empty";

            }

            else {

                for (int i = 1; i < size*2; i++) { os << "_"; }

                os << std::endl;

                std::string queue_string = "";

                auto current = queue._front;

                for(; current; current = current->previous) {

                    queue_string =  std::to_string(current->data) +  " " + queue_string;

                }

                os << queue_string << std::endl;

                for (int i = 1; i < size*2; i++) { os << "_"; }

            }



            return os;

        }

};



int main()

{

    Queue queue;



    queue.push_back(9);

    queue.push_back(8);

    queue.push_back(7);

    queue.push_back(6);

    queue.push_back(5);



    std::cout << queue << std::endl;

    std::cout << "back is " << std::to_string(queue.get_back()) << 'n';

    std::cout << "front is " << std::to_string(queue.get_front()) << 'n';

    std::cout << "size is " << std::to_string(queue.get_size()) << "nn";



    queue.pop_front();

    queue.pop_front();

    queue.pop_front();



    std::cout << queue << std::endl;

    std::cout << "back is " << std::to_string(queue.get_back()) << 'n';

    std::cout << "front is " << std::to_string(queue.get_front()) << 'n';

    std::cout << "size is " << std::to_string(queue.get_size()) << "nn";



    queue.pop_front();

    queue.pop_front();



    std::cout << queue << std::endl;

    std::cout << "back is " << std::to_string(queue.get_back()) << 'n';

    std::cout << "front is " << std::to_string(queue.get_front()) << 'n';

    std::cout << "size is " << std::to_string(queue.get_size()) << "nn";



    queue.pop_front();

}