给定一个单链表，请把这个链表翻转下。

示例：输入 1->2->3  输出 1<-2<-3

class Node:
    def __init__(self, value=None, next=None)
        self.value = None
        self.next = None

def reverse_linked_list(node):
    if node.next == None:
        return None

    cur_ptr, last_ptr = node, Node()
    while cur_ptr != None:
        temp_ptr = cur.next
        cur.next = last_ptr
        
        last_ptr = cur
        cur_ptr = temp_ptr