linked_list_2020_start

// linked_list.h

#ifndef LINKED_LIST_H_INCLUDED
#define LINKED_LIST_H_INCLUDED

// note: implementation required for pass

class linked_list
{
   linked_list(linked_list &&rhs) = delete;
   linked_list(const linked_list &rhs) = delete;
   linked_list &operator=(const linked_list &rhs) = delete;

public:
   linked_list();
   ~linked_list();

   void push_front(int value);
   void push_back(int value);
   void insert(int value, int index);
   void pop_front();
   void pop_back();
   void remove(int index);
   void clear();
   int size() const;
   int front() const;
   int back() const;
   int at(int index) const;

private:
   struct node
   {
      node();
      explicit node(int value, node *next);

      int value_;
      node *next_;
   };

   int count_;
   node *head_;
   node *tail_;
};

#endif // !LINKED_LIST_H_INCLUDED

// linked_list.cpp

#include "linked_list.h"

linked_list::node::node()
   : value_(0)
   , next_(nullptr)
{

}

linked_list::node::node(int value, node *next)
   : value_(value)
   , next_(next)
{

}

linked_list::linked_list()
   : count_(0)
   , head_(nullptr)
   , tail_(nullptr)
{

}

linked_list::~linked_list()
{

}

void linked_list::push_front(int value)
{
    node* Tmp_Node;

    if (head_ != nullptr) // If the list is not empty.
    {
        Tmp_Node = head_;
        head_ = new node{ value, Tmp_Node }; // Connects the old head to the new head as the "next" node.
        count_++;
    }
    else // If the list is empty.
    {
        Tmp_Node = new node{value, nullptr };
        head_ = Tmp_Node;
        tail_ = Tmp_Node;
        count_++;
    }
}

void linked_list::push_back(int value)
{
    node* Tmp_Node;

    if (tail_ != nullptr) // If the list is not empty.
    {
        Tmp_Node = new node{ value, nullptr };
        tail_->next_ = Tmp_Node;
        tail_ = Tmp_Node;
        count_++;
    }
    else // If the list is empty.
    {
        Tmp_Node = new node{ value, nullptr };
        tail_ = Tmp_Node;
        head_ = Tmp_Node;
        count_++;
    }
}

void linked_list::insert(int value, int index)
{
    if (index >= 0 && index <= count_) // Validates index. (Range is 0 to tail + 1)
    {
        node* Tmp_Node;

        if (index == 0) // If index is head.
        {
            if (head_ == nullptr) // If list is empty.
            {
                Tmp_Node = new node{ value, nullptr };
                head_ = Tmp_Node;
                tail_ = Tmp_Node;
                count_++;
                return;
            }
            else // If list is not empty.
            {
                Tmp_Node = head_;
                head_ = new node{ value, Tmp_Node }; // Connects the old head to the new head as the "next" node.
                count_++;
                return;
            }
        }
        else if (index == count_) // If index is after tail.
        {
            Tmp_Node = new node{ value, nullptr };
            tail_->next_ = Tmp_Node;
            tail_ = Tmp_Node;
            count_++;
        }
        else // If index is in the middle.
        {
            node* Tmp_CurrentNode = head_;
            node* Tmp_PreviousNode = head_; // Initialized as head to avoid warnings.
            int IterationCounter = 0;

            while (IterationCounter != index)
            {
                if (IterationCounter == (index - 1)) // Captures the previous node.
                {
                    Tmp_PreviousNode = Tmp_CurrentNode;
                }

                Tmp_CurrentNode = Tmp_CurrentNode->next_;
                IterationCounter++;
            }

            Tmp_Node = Tmp_CurrentNode;
            Tmp_CurrentNode = new node{ value, Tmp_Node };
            Tmp_PreviousNode->next_ = Tmp_CurrentNode;
            count_++;
        }
    }
}

void linked_list::pop_front()
{
    if (count_ > 0) // If the list is not empty.
    {
        if (count_ == 1) // If the list has only 1 node.
        {
            delete head_;
            head_ = nullptr;
            tail_ = nullptr;
            count_--;
            return;
        }
        else // If the list has more than 1 node.
        {
            node* Tmp_Node;
            Tmp_Node = head_->next_;
            delete head_;
            head_ = Tmp_Node;
            count_--;
            return;
        }
    }
}

void linked_list::pop_back()
{
    if (count_ > 0) // If the list is not empty.
    {
        if (count_ == 1) // If the list has 1 node.
        {
            delete tail_;
            tail_ = nullptr;
            head_ = nullptr;
            count_--;
            return;
        }
        else // If list has more than 1 node.
        {
            node* Tmp_CurrentNode = head_;
            node* Tmp_PreviousNode = head_; // Initialized as head just to avoid warnings.
            int IterationCounter = 0;

            while (Tmp_CurrentNode != tail_)
            {
                if (IterationCounter == (count_ - 2)) // Captures the before last node.
                {
                    Tmp_PreviousNode = Tmp_CurrentNode;
                }

                Tmp_CurrentNode = Tmp_CurrentNode->next_;
                IterationCounter++;
            }

            delete Tmp_CurrentNode;
            Tmp_PreviousNode->next_ = nullptr;
            tail_ = Tmp_PreviousNode;
            count_--;
            return;
        }
    }
}

void linked_list::remove(int index)
{
    if (index >= 0 && index < count_) // Validates if index exists in the list.
    {
        node* Tmp_Node;

        if (index == 0) // If index is head.
        {
            if (head_->next_ == nullptr) // If there is nothing after the head.
            {
                delete head_;
                head_ = nullptr;
                tail_ = nullptr;
                count_--;
                return;
            }
            else // If there is something after the head.
            {
                Tmp_Node = head_->next_;
                delete head_;
                head_ = Tmp_Node;
                count_--;
                return;
            }
        }

        node* Tmp_CurrentNode = head_;
        node* Tmp_PreviousNode = head_; // Initialized as head just to avoid warnings.
        int IterationCounter = 0;

        if (index == (count_ - 1)) // If index is tail.
        {
            while (IterationCounter != index)
            {
                if (IterationCounter == (index - 1)) // Captures the previous node.
                {
                    Tmp_PreviousNode = Tmp_CurrentNode;
                }

                Tmp_CurrentNode = Tmp_CurrentNode->next_;
                IterationCounter++;
            }

            delete Tmp_CurrentNode;
            Tmp_PreviousNode->next_ = nullptr;
            tail_ = Tmp_PreviousNode;
            count_--;
            return;
        }
        else // If index is in the middle.
        {
            while (IterationCounter != index)
            {
                if (IterationCounter == (index - 1)) // Captures the previous node.
                {
                    Tmp_PreviousNode = Tmp_CurrentNode;
                }

                Tmp_CurrentNode = Tmp_CurrentNode->next_;
                IterationCounter++;
            }

            Tmp_Node = Tmp_CurrentNode->next_;
            delete Tmp_CurrentNode;
            Tmp_PreviousNode->next_ = Tmp_Node;
            count_--;
            return;
        }
    }
}

void linked_list::clear()
{
    if (count_ > 0) // If list is not empty.
    {
        node* Tmp_CurrentNode = head_;
        node* Tmp_NextNode = nullptr;

        while (count_ != 0)
        {
            Tmp_NextNode = Tmp_CurrentNode->next_; // Sets next node.
            delete Tmp_CurrentNode;
            count_--;
            Tmp_CurrentNode = Tmp_NextNode;
        }
        head_ = nullptr;
        tail_ = nullptr;
    }
}

int linked_list::size() const
{
   return count_;
}

int linked_list::front() const
{
    if (head_ != nullptr)
    {
        return head_->value_;
    }

    return -1;
}

int linked_list::back() const
{
    if (tail_ != nullptr)
    {
        return tail_->value_;
    }

    return -1;
}

int linked_list::at(int index) const
{
    if (index >= 0 && index <= (count_ - 1)) // Validates if index exists in the list.
    {
        node* Tmp_CurrentNode = head_;
        int IterationCounter = 0;

        while (IterationCounter != index) // Gets skipped if index is 0.
        {
            Tmp_CurrentNode = Tmp_CurrentNode->next_;
            IterationCounter++;
        }
        return Tmp_CurrentNode->value_;
    }

    return -1;
}