Java: Making a linked list in a while loop

Question

I am trying to make an int (like 123) into a linked list. For example: 123 would result in a linked list of 3 -> 2 -> 1. My issue is that I am able to get each part of the number(like 3 or 2) but I can't seem to make the linked list.

Here is my while Loop:

 value = Integer.parseInt(l1StrRev) + Integer.parseInt(l2StrRev);
 result = new ListNode(value % 10);
 value = value / 10;
 while(value > 0) {
 int newVal = value % 10;
 result.next = new ListNode(newVal);
 result = result.next;
 value = value / 10;
 }

I am getting back a linked-list of just one node with the most recent value.

• Nicholas K: Are you trying to use your own implementation of a LinkedList or use the one provided by java?
• Toffe1369: I am given a class: ListNode with int val, ListNode node, and a constructor

Answer 1

In your code, you are updating the "result" variable too. So when u return the "result" variable, its actually pointing to the last Node. I would suggest, before the while loop do a resultCopy = result. And then in the end return resultCopy. This way, resultCopy stores the head node of the list, and "result" acts as a temporary node as in ur code.

• Toffe1369: Thank you so much!

Answer 2

Looks like you are missing and mixed up a couple of lines. In your loop it should be something like...

• Create a new node

  Node node = new ListNode(newVal);

• Set node.next to the result

  node.next = result;

• Your result then becomes the new node above

  result = node;