Linked List insertion isn't working in for/while loop

I am learning DSA, and was trying to implement linked list but the insertion function that i wrote is not
working in a for or while loop, its not the same when i call that function outside the loop, it works that way. I am not able to figure it out, please someone help me.

#include <iostream>

class Node {

public:
  int data;
  Node *next;

  Node(int &num) {
    this->data = num;
    next = NULL;
  }
};

class LinkedList {

  Node *head = NULL;

public:
  void insert(int num) {
    Node *tmp;
    if (head == NULL) {
      head = new Node(num);
      tmp = head;
    } else {
      tmp->next = new Node(num);
      tmp = tmp->next;
    }
  }

  void printList() {
    Node *tmp = head;
    while (tmp) {
      std::cout << tmp->data << "  ";
      tmp = tmp->next;
    }
    std::cout << std::endl;
  }

  void reverseList() {
    Node *curr = head, *prev = NULL, *nextNode;
    while (curr) {
      nextNode = curr->next;
      curr->next = prev;
      prev = curr;
      curr = nextNode;
    }
    head = prev;
  }
};

int main() {
  LinkedList list1;
  // This is not working
  int num;
  while (num != -1) {
    std::cin >> num;
    list1.insert(num);
  }

  // This is working
  // list1.insert(1);
  // list1.insert(2);
  // list1.insert(3);
  // list1.insert(4);
  // list1.insert(5);

  list1.printList();
  list1.reverseList();
  list1.printList();

  return 0;
}

I expect this after insertion

>Solution :

When inserting the nth item (1st excluded) tmp is a null pointer, i don’t understand what you are doing there, you are assigning to next of some memory then you make that pointer point to another location, losing the pointer next you assigned before, you must keep track of the last item if you want optimal insertion. This way you are only assigning to some *tmp then going out of scope loses all your data… The best way is to just keep a pointer to the last inserted item, no need to use *tmp.

class LinkedList
{
   Node *head = NULL;
   Node *tail = NULL;

public:
    void insert(int num)
    {
        if (head == NULL)
        {
            head = new Node(num);
            tail = head;
        }
        else
        {
            tail->next = new Node(num);
            tail = tail->next;
        }
    }
...
}