0328.py

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

class Solution:
    def oddEvenList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if head == None or head.next == None:
            return head

        odd = head
        even = head.next
        t = even
        while even != None and even.next != None:
            odd.next = even.next
            odd = odd.next
            even.next = odd.next
            even = even.next

        odd.next = t
        return head

def createList():
    head = ListNode(0)
    cur = head
    cur.next = ListNode(0)
    cur.next.next = ListNode(1)
    cur.next.next.next = ListNode(1)
    cur.next.next.next.next = ListNode(2)
    return head
            
def printList(head):
    cur = head
    while cur != None:
        print(cur.val, '-->', end='')
        cur = cur.next

    print('NULL')

if __name__ == "__main__":
    head = createList()
    printList(head)
    res = Solution().oddEvenList(head)
    printList(res)