61. Rotate List

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

Example 1:

Input: 1->2->3->4->5->NULL, k = 2
Output: 4->5->1->2->3->NULL
Explanation:
rotate 1 steps to the right: 5->1->2->3->4->NULL
rotate 2 steps to the right: 4->5->1->2->3->NULL

Example 2:

Input: 0->1->2->NULL, k = 4
Output: 2->0->1->NULL
Explanation:
rotate 1 steps to the right: 2->0->1->NULL
rotate 2 steps to the right: 1->2->0->NULL
rotate 3 steps to the right: 0->1->2->NULL
rotate 4 steps to the right: 2->0->1->NULL

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

class Solution:
    def rotateRight(self, head, k):
        """
        :type head: ListNode
        :type k: int
        :rtype: ListNode
        """
        if head == None or k==0:
            return head
        l = 0
        start = head
        while head:
            l += 1
            head = head.next
        print(start.val)
        newstart = newend = end = start
        k = k%l
        if k==0:
            return start
        for i in range(l-1):
            end = end.next
        for i in range(l-k-1):
            newstart = newstart.next
            newend = newend.next
        newstart = newstart.next
        end.next = start
        newend.next = None
        print(l)
        print(k)
        return newstart