[leetcode]Swap Nodes in Pairs

其实头脑冷静下来 把图画一画 整条题很简单的

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public class Solution { public ListNode swapPairs(ListNode head) { if (head == null || head.next == null) return head; ListNode current = head; ListNode dummy = new ListNode(-1); dummy.next = head; ListNode previous = dummy; while (current != null && current.next != null){ previous.next = current.next; ListNode next = current.next.next; current.next.next = current; current.next = null; previous = current; current = next; } if (current != null){ previous.next = current; } return dummy.next; } }