easy

Reverse Linked List

A linked list is a data structure that consists of nodes that are linked to each other. Each node contains a value and a reference (pointer) to the next node in the list. To reverse a linked list, we need to reverse the order of the references (pointers) between the nodes.

Here is one way to implement the reverse linked list function in JavaScript:

function reverseLinkedList(head) {
  let prev = null;
  let current = head;
  let next = null;
 
  while (current !== null) {
    next = current.next;
    current.next = prev;
    prev = current;
    current = next;
  }
 
  return prev;
}

In this implementation, we use three pointers: prev, current, and next. prev is initially set to null, current is set to the head of the list, and next is set to null. We then iterate through the list using a while loop, updating the pointers as follows:

Set next to the next node in the list. Set the next property of the current node to prev. Update prev to current. Update current to next. At the end of the loop, the prev pointer will be pointing to the new head of the reversed list.

The time complexity of this implementation is O(n), where n is the number of nodes in the linked list, since we need to iterate through all the nodes once. The space complexity is O(1), since we are only using a constant amount of extra memory to store the pointers.