【LeetCode】Swap Nodes in Pairs 解题报告

【LeetCode】Swap Nodes in Pairs 解题报告

标签（空格分隔）： LeetCode

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题目地址：https://leetcode.com/problems/swap-nodes-in-pairs/description/

题目描述：

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.

Ways

交换相邻的两个链表元素。

pre -> a -> b -> b.next 转换成 pre -> b -> a -> b.next，需要修改3个指针。

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def swapPairs(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        pre, pre.next = self, head
        while pre.next and pre.next.next:
            a = pre.next
            b = a.next
            pre.next, a.next, b.next = b, b.next, a
            pre = a
        return self.next

Date

2017 年 8 月 29 日