首页 > 代码库 > leetcode 【 Swap Nodes in Pairs 】python 实现
leetcode 【 Swap Nodes in Pairs 】python 实现
题目:
Given a linked list, swap every two adjacent nodes and return its head.
For example,
Given 1->2->3->4
, you should return the list as 2->1->4->3
.
Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.
代码:oj 测试通过 Runtime: 42 ms
1 # Definition for singly-linked list. 2 # class ListNode: 3 # def __init__(self, x): 4 # self.val = x 5 # self.next = None 6 7 class Solution: 8 # @param a ListNode 9 # @return a ListNode10 def swapPairs(self, head):11 if head is None or head.next is None: 12 return head13 14 dummyhead = ListNode(0)15 dummyhead.next = head16 17 pre = dummyhead18 curr = head19 while curr is not None and curr.next is not None:20 tmp = curr.next21 curr.next = tmp.next22 tmp.next = pre.next 23 pre.next = tmp24 pre = curr25 curr = curr.next26 return dummyhead.next
思路:
基本的链表操作。
需要注意的是while循环的判断条件:先判断curr不为空,再判断curr.next不为空。
这种and判断条件具有短路功能,如果curr为空就不会进行下一个判断了,因此是安全的
leetcode 【 Swap Nodes in Pairs 】python 实现
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