reverseLinkedList.js

////////////////////////////////////////////////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]
// Example 3:
// Input: head = []
// Output: []
/**
 * 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}
 */
 const reverseList = function(head) {
    if(head === null) return head;
    let current = head, prev = null;

    while(current !== null){
        const next = current.next
        current.next = prev;
        prev = current;
        current = next;
    }
    return prev;
};

// console.log(reverseList([1,2,3,4,5]));
// console.log(reverseList([1,2]));
// console.log(reverseList([]));