append node to list

[Progesco]

Please help me find out the error in this code
Thank you

#include <iostream>

using namespace std;

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

class List
{
      private:
             Node* head;
      public:
             List() {head=NULL;}
             void appendNode (int);
             /*void sort();*/
             void display(void);
             /*void merge(List &, List&);*/
};

void List::appendNode(int num)
{
     Node* newnode;
     Node* nodeptr;
     newnode->data = num;
     newnode->next = NULL;
     
     if(head=NULL)
     {
          head = newnode;
     }
     else
     {
          nodeptr = head;
          while(nodeptr->next!=NULL)
          {
               nodeptr = nodeptr->next;
          }
          nodeptr->next = new Node();
          nodeptr->next->data = num;
     }
}

void List::display()
{
     int count = 0;
     Node* currNode = head;
     while (currNode!=NULL)
     {
           cout << currNode->data << " ";
           currNode = currNode->next;
           count++;
     }
     cout << "\nNumber of nodes in the list: " << count << endl;
}

int main()
{
    List list1;
    list1.appendNode(9);
    list1.appendNode(4);
    list1.appendNode(3);
    list1.appendNode(12);
    list1.appendNode(100);
    list1.display();
    
    getchar();
    return 0;
}
     
             

[MaikCAE]

Which errors you get?

two things I've seen:

- in appendNode Node* newnode;-> newnode is just setted and never used (it's not an error but you
can erase it)

- I'm not sure but I think for nodeptr->next = new Node(); you need a constructor and later a destructor in public part of Node class

[luckyxv]

- In void List::appendNode(int num) method, you need to allocate memory for the new node, even for the first one (head) :

Node* newnode = new Node(); instead of Node* newnode;

- Then, you have a classical test error (assignment instead of equality test) :
if(head=NULL) should be if(head==NULL)

- And finally, you can use the previously created/allocated newnode variable :
nodeptr->next = newnode; instead of nodeptr->next = new Node();

You can comment //nodeptr->next->data = num; . It's no use then ... You previously set data for newnode.

[Progesco]

thank, it worked