【LEETCODE】61- Rotate List [Python]__Python

Given a list, rotate the list to the right by k places, where k is non-negative.

For example:

Given 1->2->3->4->5->NULL and k = 2,

return 4->5->1->2->3->NULL.

題意：

給一個list，向右輪換k個位置，k非負

思路：

觀察到變化的主要是head，先得到list的長度，再得到新head的位置，做出變化

Python

# Definition for singly-linked list.# class ListNode(object):#     def __init__(self, x):#         self.val = x#         self.next = Noneclass Solution(object):    def rotateRight(self, head, k):        """        :type head: ListNode        :type k: int        :rtype: ListNode        """                if head is None:            return None                if k==0:            return head                    dummy=ListNode(0)        dummy.next=head        p=dummy        length=0                while p.next:                       # 得到list的長度            length+=1            p=p.next                p.next=dummy.next                step=length-(k%length)              # 得到新head的位置                while step>0:                       # 到新head的位置            step-=1            p=p.next                dummy.next=p.next                   # 變化        p.next=None                return dummy.next