【LeetCode】92. Reverse Linked List II 解题报告(Python)
标签(空格分隔): LeetCode
作者: 负雪明烛
id: fuxuemingzhu
个人博客: http://fuxuemingzhu.me/
题目地址:https://leetcode.com/problems/reverse-linked-list-ii/description/
题目描述:
Reverse a linked list from position m to n. Do it in one-pass.
Note: 1 ≤ m ≤ n ≤ length of list.
Example:
Input: 1->2->3->4->5->NULL, m = 2, n = 4
Output: 1->4->3->2->5->NULL
题目大意
把单链表中第m–n个元素进行翻转。
解题方法
其实就是翻转链表的而变形题目了。做法大家都能想出来,进行一遍遍历,把第m到n个元素进行翻转,即依次插入到第m个节点的头部。这个题还是有意思的。建议后面再多做几遍。
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution(object):
def reverseBetween(self, head, m, n):
"""
:type head: ListNode
:type m: int
:type n: int
:rtype: ListNode
"""
count = 1
root = ListNode(0)
root.next = head
pre = root
while pre.next and count < m:
pre = pre.next
count += 1
if count < m:
return head
mNode = pre.next
curr = mNode.next
while curr and count < n:
next = curr.next
curr.next = pre.next
pre.next = curr
mNode.next = next
curr = next
count += 1
return root.next
日期
2018 年 6 月 24 日 ———— 今天请客吃了海底捞~