Stack System

The stack system uses linked lists to create a ‘stack’ of items.

It follows the FILO (First In, Last Out) paradigm.

/* Stack
 *
 * Description:
 * A stack is a first-in-last-out system.
 */

#include <iostream>

class Node
{
public:
  int value = 0;
  Node *prev = nullptr;

  Node(int val) : value(val), prev(nullptr) {}
};

class Queue
{
public:
  Node *tail = nullptr;

  // Queue the item
  void enqueue(int item)
  {
    Node *node = new Node(item);
    node->value = item;

    // If the tail do not exist the
    // node array size is zero.
    if (tail == nullptr)
    {
      tail = node;
      return;
    }

    // If a value does exist. Then add the
    // item to the queue.
    node->prev = tail;
    tail = node;
  }

  // Deque item
  void deque()
  {
    // If tail exists do this
    if (tail != nullptr)
    {
      Node *current_tail = tail;
      tail = tail->prev;

      // Clean up
      delete current_tail;
    }
  }

  // Display values
  void display()
  {
    Node *current = tail;
    while (current != nullptr)
    {
      std::cout << current->value << " " << std::endl;
      current = current->prev;
    }
  }
};

int main(void)
{
  Queue queue;
  queue.enqueue(1);
  queue.enqueue(2);
  queue.enqueue(3);
  queue.enqueue(4);

  queue.deque();
  queue.deque();

  queue.display();
  return 0;
}