题目：分割链表

class Solution:
    def partition(self, head: ListNode, x: int) -> ListNode:
        p=less=ListNode(0)
        q=more=ListNode(0)

        while head:
            if head.val<x:
                less.next=head
                less=less.next
            else:
                more.next=head
                more=more.next
            head=head.next
        # 链表的最后都需要指向None，这个代表链表的结束
        more.next=None
        less.next=q.next
        return p.next