Skip to content
On this page

24. 两两交换链表中的节点

给你一个链表,两两交换其中相邻的节点,并返回交换后链表的头节点。你必须在不修改节点内部的值的情况下完成本题(即,只能进行节点交换)。

示例 1:
输入:head = [1,2,3,4]
输出:[2,1,4,3]

示例 2:
输入:head = []
输出:[]

示例 3:
输入:head = [1]
输出:[1]

提示:
链表中节点的数目在范围 [0, 100] 内
0 <= Node.val <= 100

javascript
/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var swapPairs = function(head) {
  if(!head || (head && !head.next)){
    return head
  }
  const next = head.next
  head.next = swapPairs(next.next)
  next.next = head
  return next
}

// test
function ListNode(val, next) {
  this.val = val === undefined ? 0 : val
  this.next = next === undefined ? null : next
}

var l1 = new ListNode(1)
var lstNode1 = new ListNode(2)
var lstNode2 = new ListNode(3)
var lstNode3 = new ListNode(4)
l1.next = lstNode1
lstNode1.next = lstNode2
lstNode2.next = lstNode3

console.log(swapPairs(l1))