cpa_lab_5_3_13_(4)-B.cpp

#include <iostream>

using namespace std;

class Node
{
    public:
        Node(int val);
        int value;
        Node* next;
};

Node::Node(int val) : value(val), next(nullptr){}

class List{
    public:
        List();
        void push_front(int value);
        bool pop_front(int &value);
        void push_back(int value);
        int size();
    private:
        Node* head;
        Node* tail;
};

List::List() : head(nullptr), tail(nullptr){}

void List::push_front(int value)
{
    Node* new_head = new Node(value);
    new_head->next = head;

    if(head == nullptr)
        tail = new_head;

    head=new_head;
}

bool List::pop_front(int &value)
{
    if(head == nullptr)
        return false;

    value = (*head).value;
    head = (*head).next;
    return true;
}

void List::push_back(int value)
{
    if(head != nullptr)
    {
        Node* new_tail = new Node(value);
        tail->next = new_tail;
        tail = new_tail;
    }
    else push_front(value);
}

int List::size()
{
    int i = 0;
    for(Node* iter = head; iter != nullptr; iter = iter->next, ++i);
    return i;
}

int main()
{
    List list;

    list.push_back(1);
    list.push_back(2);
    list.push_back(3);
    list.push_back(4);
    int value = 0;

    while (list.pop_front(value))
    {
        cout << value << endl;
    }
    return 0;
}