lc206. Reverse Linked List

206. Reverse Linked List Reverse a singly linked list.

Example:

Input: 1->2->3->4->5->NULL Output: 5->4->3->2->1->NULL Follow up:

A linked list can be reversed either iteratively or recursively. Could you implement both?

思路:一节节断开？

代码:python3

class Solution:
    def reverseList(self, head: ListNode) -> ListNode:
        pointer = None
        while head:
            prev = head
            head = head.next
            prev.next = pointer
            pointer = prev
        return pointer