Leetcode 206. Reverse Linked List 链表翻转 Python 两种解法

问题描述

Reverse a singly linked list. 翻转一个链表

#1

第一种方法：迭代

代码语言：javascript复制

class ListNode(object):
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution(object):
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        pre = cur = None
        if head:
            pre = head
            cur = head.next
            pre.next = None
        else:
            return None
        while cur:
            p = cur
            cur = cur.next
            p.next = pre
            pre = p
        return pre

#2

第二种方法：递归

代码语言：javascript复制

class ListNode(object):
    def __init__(self, x):
        self.val = x
        self.next = None
class Solution:
    def reverseList(self, head):
        return reverse(head)

    def reverse(self, node, prev=None):
        if not node:
            return prev
        n = node.next
        node.next = prev
        return reverse(n, node)

list 递归 链表

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