https://leetcode.com/problems/swap-nodes-in-pairs/ 1. 2022.02.05 시도 소요시간: 10분 class Solution { public ListNode swapPairs(ListNode head) { if (head == null || head.next == null) { return head; } ListNode prev = new ListNode(); ListNode ret = prev; prev.next = head; while (prev.next != null && prev.next.next != null) { ListNode temp = head.next; head.next = temp.next; temp.next = head; prev.next =..