C++ linked list weird outputs

So i've been trying to code a linked list. When i debug or if i put one more print statement like this;

intlist.add_node(7);
intlist.print_list();
intlist.add_node(8);

It works fine prints;

5
7
5
7
8

But if i remove that statement, it only prints three eights. Same goes for debugging, it seems working but if i just run it doesn't. I didn't understand what is wrong. Here's my main;

int main(){
  Linked_list intlist;
  intlist.add_node(5);
  intlist.add_node(7);
  intlist.print_list();
  intlist.add_node(8);
  intlist.print_list();
  return 0;
}

header;

class Linked_list{
public:
  Linked_list();

  void add_node(int data);
  void remove_node(int data);
  int get_data(int index);
  void print_list();

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

  Node* head;
  int lenght;
};

And header's source file;

Linked_list::Linked_list(){
  head = 0;
  lenght = 0;
}

void Linked_list::add_node(int data){
  Node* newnode = new Node;
  newnode->data = data;
  newnode->next = NULL;
  if (head == 0) {head = newnode; lenght = 1; return;}
  else{
      Node* temp = new Node;
      temp = head;
      while (temp->next != NULL){
          temp = temp->next;

      }
      lenght++;
      temp->next = newnode;
      delete temp;
  }
}


void Linked_list::remove_node(int data){
    return;
}

int Linked_list::get_data(int index){
    return 0;
}

void Linked_list::print_list(){
    if (head == 0) {std::cout << "List is empty!!" << std::endl; 
    return;}
    else{
        Node* ptr = new Node;
        ptr = head;
        for (int i = lenght; i > 0; i--){
            std::cout << ptr->data << std::endl;
            ptr = ptr->next;
        }
    }
}