题目链接

思路

使用一个节点一直位于交换的两个节点的前面一个节点即可

代码

class Solution {
    fun swapPairs(head: ListNode?): ListNode? {
        if (head?.next == null) return head
        val tmpHead = ListNode(0)
        var curr = tmpHead
        var firstN = head
        var secondN = head.next
        while (firstN!!.next != null) {
            firstN.next = secondN!!.next
            secondN.next = firstN
            curr!!.next = secondN
            curr = firstN
            if (firstN.next != null) {
                firstN = firstN.next
                secondN = firstN!!.next
            }
        }
        return tmpHead.next
    }
}