题目描述:
给定一个链表,两两交换其中相邻的节点,并返回交换后的链表。
你不能只是单纯的改变节点内部的值,而是需要实际的进行节点交换。
示例:
给定 1->2->3->4, 你应该返回 2->1->4->3.
解题思路:
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution:
def swapPairs(self, head: ListNode) -> ListNode:
output = ListNode(0)
tmp = output
if head == None or head.next == None:
return head
first, second = head, head.next
while(first or second):
if second:
tmp.next = second
tmp = tmp.next
first.next = tmp.next
tmp.next = first
tmp = tmp.next
if tmp.next:
first = tmp.next
else:
first = None
break
if tmp.next.next:
second = tmp.next.next
else:
second = None
return output.next
算法性能: