328. Odd Even Linked List——多利用fake

Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.

You should try to do it in place. The program should run in O(1) space complexity and O(nodes) time complexity.

Example:
Given 1->2->3->4->5->NULL,
return 1->3->5->2->4->NULL.

Note:
The relative order inside both the even and odd groups should remain as it was in the input.
The first node is considered odd, the second node even and so on ...

# Definition for singly-linked list.

# class ListNode(object):

#     def __init__(self, x):

#         self.val = x

#         self.next = None

class Solution(object):

    def oddEvenList(self, head):

        """

        :type head: ListNode

        :rtype: ListNode

        """

        node = head

        i = 1

        odd_fake, even_fake = ListNode(None), ListNode(None)

        odd_tail, even_tail = odd_fake, even_fake

        while node:

            if i & 1:

                odd_tail.next = node

                odd_tail = node

            else:

                even_tail.next = node

                even_tail = node

            node = node.next

            i += 1

        even_tail.next = None

        odd_tail.next = even_fake.next

        return odd_fake.next

巴特西

328. Odd Even Linked List——多利用fake_head

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