/** * Definition for singly-linked list. * function ListNode(val, next) { * this.val = (val===undefined ? 0 : val) * this.next = (next===undefined ? null : next) * } */ class ListNode { constructor(val, next) { this.val = (val === undefined ? 0 : val); this.next = (next === undefined ? null : next); } } /** * @param {ListNode} head * @return {ListNode} */ const reverseList = (head) => { let dummy = new ListNode(), new_head = dummy; while (head !== null) { dummy.next = new ListNode(head.val, dummy.next); head = head.next; } return new_head.next; };