To solve this problem, we'll use a curr pointer that will start at head.

We will traverse the linked list and adjust the next pointer of a given node so that it skips over the immediate next node. We can accomplish this via curr.next = curr.next.next. This operation effectively removes the node referenced by curr.next from the linked list by bypassing it.

After performing this removal, we'll move curr forward to continue the process from the newly adjusted position in the list (curr = curr.next). This step is crucial as it maintains the continuity of the traversal, essentially moving the point of operation one step ahead in the list.

The process concludes when we encounter a scenario where curr or curr.next is null, indicating we have reached the end of the list or there are no more nodes to skip. Finally, we can return the head node, which is the starting point of the modified list.

Let's see this visually:

We are given a linked list 1 -> 2 -> 3 -> 4 -> 5, and our goal is to remove every second node, resulting in the list 1 -> 3 -> 5.

Initializing the Necessary Variables

For this problem, we only need to introduce one additional variable, curr, which will keep track of the current node in the list. We will initialize curr to the head node. It's important to note that we cannot use the head node for tracking purposes because if we were to move its reference, we would lose the reference to the head node (the node with the value 1 in this case).

Step 1

We are starting with both head and curr pointing at the node 1.

Since we want to skip the second node, we need to adjust the link so that curr.next points tocurr.next.next.

After we do this, we only need to slide the curr pointer (curr = curr.next). curr.next previously referenced the node with value 2, but now that we've deleted this node, curr.next references the node with value 3.

Step 2

Our work for the second iteration is much the same. curr references the node with value 3.

We want to skip the second node, so we need to adjust the link so that curr.next points tocurr.next.next.

After we do this, we slide the curr pointer (curr = curr.next).

Step 3

We have reached the condition where curr.next is pointing to null.

Therefore, we exit the loop and return the head node which is our result list 1 -> 3 -> 5 -> null.

Solution Code

function removeEverySecondNode(head) {
  let curr = head;
  while (curr && curr.next) {
    curr.next = curr.next.next;
    curr = curr.next;
  }
  return head;
}