Fila/queue.cpp at main · FernandoCesarMS/Fila · GitHub

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#include "queue.h"

struct Node
{
  int key;
  Node *next;
};

Queue::Queue()
{
  this->front_ = nullptr;
  this->back_ = nullptr;
}

void Queue::push(int k)
{
  if (this->count() == 0)
  {
    Node *x = new Node;
    x->key = k;
    x->next = nullptr;
    this->front_ = x;
    this->back_ = x;
  }
  else
  {
    Node *x = new Node{k, nullptr};
    this->back_->next = x;
    this->back_ = x;
  }
}

void Queue::pop()
{
  if (this->count() == 0)
  {
    throw EmptyException();
  }
  else if (this->count() == 1)
  {
    this->front_ = this->back_ = nullptr;
  }
  else
  {
    Node *x = new Node{this->front_->next->key, this->front_->next->next};
    this->front_ = x;
  }
}

int Queue::front() const
{
  if (this->count() == 0)
  {
    throw EmptyException();
  }
  else
  {
    return this->front_->key;
  }
}

int Queue::back() const
{
  if (this->count() == 0)
  {
    throw EmptyException();
  }
  else
  {
    return this->back_->key;
  }
}

int Queue::count() const
{
  Node *end = this->front_;
  int tamanho = 0;
  while (end != nullptr)
  {
    tamanho++;
    end = end->next;
  }
  return tamanho;
}