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

class LinkedList(object):
    def get_middle(self, head: ListNode) -> ListNode:
        fast = slow = head
        while fast and fast.next:
            slow = slow.next
            fast = fast.next.next
        return slow
    
    def reverse(self, head: ListNode) -> ListNode:
        prev, cur = None, head
        while cur:
            prev, cur.next, cur = cur, prev, cur.next
        return prev