LeetCode：61. 旋转链表

1、题目描述

给定一个链表，旋转链表，将链表每个节点向右移动 k 个位置，其中 k 是非负数。

示例 1:

输入: 1->2->3->4->5->NULL, k = 2
输出: 4->5->1->2->3->NULL
解释:
向右旋转 1 步: 5->1->2->3->4->NULL
向右旋转 2 步: 4->5->1->2->3->NULL

示例 2:

输入: 0->1->2->NULL, k = 4
输出: 2->0->1->NULL
解释:
向右旋转 1 步: 2->0->1->NULL
向右旋转 2 步: 1->2->0->NULL
向右旋转 3 步: 0->1->2->NULL
向右旋转 4 步: 2->0->1->NULL

2、题解

2.1、解法一

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def rotateRight(self, head, k):
        """
        :type head: ListNode
        :type k: int
        :rtype: ListNode
        """
        node = ListNode(0)
        node.next = head
        if head == None:
            return None
        elif head.next == None:
            return head

        count = 0
        cur = node.next
        while cur:
            cur = cur.next
            count += 1
        i = 0
        k = k%count
        while i < k:
            cur = node.next
            prev = cur
            while cur.next:
                prev = cur
                cur = cur.next
            cur.next = node.next
            node.next = cur
            prev.next = None
            i += 1
        return node.next