Insert a Node at specific Position in a Singly Linked List in C++

// Linked List Insertion at a specific position in C++
#include<iostream>
using namespace std;

class Node
{
public:
  int data;
  Node *next;
};

// Create a global variable for the size of the Linked List
int listSize = 0; // Rename the global size variable

void insert(Node **head, int data)
{
  Node *new_node = new Node();
  new_node->data = data;
  new_node->next = *head;
  *head = new_node;
  listSize++; // Update the global size variable
}

// Method to insert at a given position
void insertPosition(int pos, int data, Node **head)
{
  Node *new_node = new Node();
  new_node->data = data;
  new_node->next = nullptr;

  // Invalid positions
  if (pos < 1 || pos > listSize + 1) // Use listSize instead of size
  {
    cout << "Invalid" << endl;
    return;
  }

  // Inserting as the first node
  if (pos == 1)
  {
    new_node->next = *head;
    *head = new_node;
    listSize++; // Update the global size variable
  }
  else
  {
    Node *temp = *head;

    // Traverse to the current (pos-1)th node
    while (--pos > 1)
    {
      temp = temp->next;
    }

    new_node->next = temp->next;
    temp->next = new_node;
    listSize++; // Update the global size variable
  }
}

void display(Node *node)
{
  cout << "Linked List: ";

  while (node != nullptr)
  {
    cout << node->data << " ";
    node = node->next;
  }

  cout << endl;
}

int main()
{
  Node *head = nullptr;

  insert(&head, 140);
  insert(&head, 120);
  insert(&head, 80);
  insert(&head, 60);
  insert(&head, 20);

  display(head);

  insertPosition(2, 40, &head);

  insertPosition(5, 100, &head);

  insertPosition(8, 160, &head);

  display(head);

  return 0;
}