python如何实现单向链表及单向链表的反转

class Listnode:
  def __init__(self, val):
    self.val = val
    self.next = None

 first_node = ListNode("A")
 second_node = ListNode("B")
 third_node = ListNode("C")
 first_node.next = second_node
 second_node.next = third_noe

class Solution:
  def reverse(self, head):
    prev = None
    current = head
    while current:
      middle, current.next = current.next, prev
      prev, current = current, middle
    return prev

solution = Solution()
result = solution.reverse(first_node)

print(result.val, result.next.val, result.next.next.val)