61. Rotate List

Problem Link

Description

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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

Solution

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Python3

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def rotateRight(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
        if not head or not head.next: return head
        
        length = 1
        curr = head
        
        while curr.next:
            length += 1
            curr = curr.next
        
        k %= length
        curr.next = head
        
        for _ in range(length - k):
            curr = curr.next
        
        head = curr.next
        curr.next = None
        
        return head