边工作边刷题：70天一遍leetcode: day 27-2

Rotate List

错误点

• 因为开始要计算结点数，要遍历list，所以顺便先把tail和head连上
• 因为指针最后要落在最后一个list结点，所以移动n-1步，初始的步数为1（即开始已经计入head）。同理，第二次移动n-k-2步到新head的前一个结点，断开
• n-k%n!=(n-k)%n，比如n=2, k=2 n-k%n=2, (n-k)%n=0

# 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
        """
        if not head or k==0: return head
        cur = head
        n=1
        while cur.next:
            cur=cur.next
            n+=1
        
        n = n-k%n
        cur.next = head
        cur = head
        while n-1>0:
            cur=cur.next
            n-=1

        next = cur.next
        cur.next=None
        return next