Reverse Linked List

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]

 

 

/**
 * 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 dummy = head;
    let reversePrevious = null;
    let reverseNext = null;
    while(dummy){
        reversePrevious = dummy.next;
        dummy.next = reverseNext;
        reverseNext = dummy;
        dummy = reversePrevious;
    }
    
    return reverseNext;
};