golang力扣leetcode 24.两两交换链表中的节点

package main
type ListNode struct {
  Val  int
  Next *ListNode
}
func swapPairs1(head *ListNode) *ListNode {
  if head == nil || head.Next == nil {
    return head
  }
  newHead := head.Next
  newHeadNext := newHead.Next
  newHead.Next = head
  head.Next = swapPairs1(newHeadNext)
  return newHead
}
func swapPairs2(head *ListNode) *ListNode {
  dummy := &ListNode{0, head}
  cnt := dummy
  for cnt.Next != nil && cnt.Next.Next != nil {
    node1 := cnt.Next
    node2 := cnt.Next.Next
    cnt.Next = node2
    node1.Next = node2.Next
    node2.Next = node1
    cnt = node1
  }
  return dummy.Next
}