24. 两两交换链表中的节点 @Python @Go

原题

https://leetcode.cn/problems/swap-nodes-in-pairs/description/

思路

虚拟节点

复杂度

时间：O(n)
空间：O(n)

Python代码

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def swapPairs(self, head: Optional[ListNode]) -> Optional[ListNode]:
        node0 = dummy = ListNode(next = head)
        node1 = head 
        while node1 and node1.next:
            node2 = node1.next 
            node3 = node2.next 
            # 两两交换
            node0.next = node2
            node2.next = node1
            node1.next = node3
            # 移动指针
            node0 = node1 
            node1 = node3 
        return dummy.next
        

Go代码

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func swapPairs(head *ListNode) *ListNode {
    // 虚拟节点指针
	dummy := &ListNode{Next: head}
	node0 := dummy
	node1 := head
	for node1 != nil && node1.Next != nil {
		node2 := node1.Next
		node3 := node2.Next
		// 两两交换
		node0.Next = node2
		node2.Next = node1
		node1.Next = node3
		// 移动指针
		node0 = node1
		node1 = node3
	}
	return dummy.Next
}