leetcode-mid-Linked list-328 Odd Even Linked List-NO

mycode

# 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
        """
        Odd = head
        Even = dummyeven = head.next
        while Even and Even.next:
            print(Even.val,Odd.val,Odd.next.val,Odd.next.next.val)
            Even.next = Even.next.next #3 6 7
            print(Even.next.val,Odd.next.val,Odd.next.next.val)
            Even = Even.next
            Odd.next = Odd.next.next # 5 4 Null
            print(Odd.next.val,Odd.next.val,Odd.next.next.val)
            Odd = Odd.next
            print(Even.val,Odd.val)
        Odd.next = dummyeven #因为无论even=None还是Even.next=None,其实在没有Even = Even.next之前，Even.next=head链中它的下一个，所以不用分类讨论加不加None

        return head
    

错误原因：Even节点变化之后，Odd取next和.next.next时，链表都已经变化了

参考：保证链表取值过程中相对顺序不乱！

# 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
        """
        if not head:
            return head
        Odd = head
        Even = dummyeven = head.next
        while Even and Even.next:
            Odd.next = Even.next
            Odd = Odd.next
            Even.next = Odd.next #3 6 7
            Even = Even.next
        Odd.next = dummyeven #因为无论even=None还是Even.next=None,其实在没有Even = Even.next之前，Even.next=head链中它的下一个，所以不用分类讨论加不加None
        return head