def answer3(a): #使用快慢指针来均分链表， 然后把后面一半倒序, 拆分为2个队列，上看去更简洁
slow = fast = a.first
pre = None
while fast:
pre = slow
slow = slow.next
if fast.next:
fast = fast.next.next
else:
fast = fast.next
if fast == a.last:
break;
pre.next = None
a.last = pre
b = Queue()
while slow:
b.add(slow)
slow = slow.next
import reverse_list
b2 = reverse_list.answer(b)
r = Queue()
while a.element() and b.element() :
r.add(Node(a.remove().value))
r.add(Node(b.remove().value))
if b.element():
r.add(Node(b.remove().value))
return r
