328.py

'''
 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.
'''

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

classSolution(object):
defoddEvenList(self, head):
"""
 :type head: ListNode
 :rtype: ListNode
 """
ifnothead:
returnNone

odd, even=head, head.next
evenHead=even
whileevenandeven.next:
odd.next=even.next
odd=odd.next
even.next=odd.next
even=even.next

odd.next=evenHead
returnhead