61. Rotate List

61. Rotate List

Medium

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Given the head of a linked list, rotate the list to the right by k places.

 

Example 1:

Input: head = [1,2,3,4,5], k = 2
Output: [4,5,1,2,3]

Example 2:

Input: head = [0,1,2], k = 4
Output: [2,0,1]

 

Constraints:

• The number of nodes in the list is in the range [0, 500].
• -100 <= Node.val <= 100
• 0 <= k <= 2 * 109

 # Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:

    def get_size(self, head):
        size = 1;
        node = head
        while node:
            if node.next == None:
                node.next = head
                break
            node = node.next
            size+=1
        return size

    def rotateRight(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
        if k == 0:
            return head

        if not head:
            return head
        elif not head.next:
            return head
        size = self.get_size(head)
        target_pos = size - (k % size)-1


        node = head
        for i in range(target_pos):
            node = node.next

        new_head = node.next
        node.next = None

        return new_head