题解 | 链表：BM1 反转链表

核心代码模式

# class ListNode:
#     def __init__(self, x):
#         self.val = x		#取当前节点的值
#         self.next = None	#指向下一个节点
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param head ListNode类 
# @return ListNode类
#
class Solution:
    def ReverseList(self , head: ListNode) -> ListNode:
        # write code here
        prev = None
        curr = head
        while curr :
            nxt = curr.next #暂存下一个节点
            curr.next = prev    #反转指针
            prev = curr #反转指针
            curr = nxt  #curr前进
        return prev

测试示例

#构造链表 1->2->3
head = ListNode(1)
head.next = ListNode(2)
head.next.next = ListNode(3)

sol = Solution()
new_head = sol.ReverseList(head)
#打印反转后的链表
res = []
while new_head:
	res.append(new_head.val)
	new_head = new_head.next
print(res)