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Reverse Linked List

Problem statement​

Given the head of a singly linked list, reverse the list, and return the reversed list.

Example 1:

Input: head = [1,2,3,4,5]Output: [5,4,3,2,1]

Example 2:

Input: head = [1,2]Output: [2,1]

Example 3:

Input: head = []Output: []

Constraints:

  • The number of nodes in the list is the range [0, 5000].
  • -5000 <= Node.val <= 5000

Follow up: A linked list can be reversed either iteratively or recursively. Could you implement both?

My solution​

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function(head) {
    let current = head;
    let prevNode = null;
    let nextNode = null;
    
    while (current) {
        nextNode = current.next;
        
        current.next = prevNode;
        prevNode = current;
        current = nextNode;
    }
    
    return prevNode;
};