C++ Linked list only print the first 3 nodes - c++

Question

When you run the code, it won't print anything unless when you run it with 3 appends. Why is that? Inside the code, I added cout statement to check if it ran and when I appended 4 things to the linked list, it only ran once in the append function. But when I ran it with only 3 things appended to the list, it displayed the cout statement 3x.
main.cpp:
#include <iostream>
#include "node.h"
using namespace std;
int main()
{
LL list;
list.append("jack","2");
list.append("jack","1");
list.append("jack","3");
list.append("jack","4");
//list.insertatBegin("notjack","0");
list.print();
}
node.cpp:
#include <iostream>
using namespace std;
#include "node.h"
LL::LL()
{
head = nullptr;
}
void LL::append(string pName,string phone)
{
Node *nodePtr;
if (head == nullptr)
{
head = new Node;
head->name = pName;
head->phoneNumber = phone;
head->next = nullptr;
}
else
{
nodePtr = head;
while(nodePtr->next !=nullptr)
{
nodePtr = nodePtr->next;
}
nodePtr->next = new Node;
nodePtr->next->name = pName;
nodePtr->next->phoneNumber = phone;
nodePtr->next->next = nullptr;
}
}
void LL::print()
{
//cout << "ran" <<endl;
Node *nodePtr;
nodePtr = head;
while (nodePtr == nullptr)
{
cout << nodePtr ->name << " " << nodePtr->phoneNumber <<endl;
nodePtr = nodePtr->next;
}
}
node.h:
#ifndef NODE_H
#define NODE_H
#include <iostream>
using namespace std;
class Node
{
public:
string name; //data
string phoneNumber;
Node* next; //pointer to next
};
class LL
{
private:
Node* head; // list header
public:
LL();
void append(string pName,string phone);
void insertatBegin(string pName,string phone);
void print();
};
#endif

Answer 1

There are 2 problems with your code:
append() has undefined behavior, because newNode is uninitialized. Its value is indeterminate, causing it to point at random memory. You are not pointing it to a valid new'ed instance of Node before trying to populate it.
print() is not looping through the list at all.
Try this:
void LL::append(string pName,string phone)
{
Node *newNode = new Node; // <-- notice 'new'!
// these assignments really should be handled by a constructor...
newNode->name = pName;
newNode->phoneNumber = phone;
newNode->next = nullptr;
if (head == nullptr)
// better: if (!head)
{
cout << "it ran" <<endl;
head = newNode;
}
else
{
cout << "it ran2" <<endl;
Node *nodePtr = head;
while (nodePtr->next != nullptr)
// better: while (nodePtr->next)
{
nodePtr = nodePtr->next;
}
nodePtr->next = newNode;
}
}
void LL::print()
{
//cout << "ran" <<endl;
Node *nodePtr = head;
while (nodePtr != nullptr) // <-- '!=', not '=='
// better: while (nodePtr)
{
cout << nodePtr ->name << " " << nodePtr->phoneNumber << endl;
nodePtr = nodePtr->next;
}
}
That said, append() can be simplified a bit more:
class Node
{
public:
string name; //data
string phoneNumber;
Node* next = nullptr; //pointer to next
Node(string pName, string phone) : name(pName), phoneNumber(phone) {}
};
void LL::append(string pName,string phone)
{
Node *newNode = new Node(pName, phone);
Node **nodePtr = &head;
while (*nodePtr)
{
nodePtr = &((*nodePtr)->next);
}
*nodePtr = newNode;
// Alternatively:
/*
Node **nodePtr = &head;
while (*nodePtr)
{
nodePtr = &((*nodePtr)->next);
}
*nodePtr = new Node(pName, phone);
*/
}

Answer 2

For starters your newNode pointer does not point to anything and you are assigning to uninitialized variables name, phonenumber and next.
Node *nodePtr;
newNode->name = pName;
newNode->phoneNumber = phone;
newNode->next = nullptr;