Rotates a linked list right by k places by making it circular and cutting at the new tail; O(n).
## What is it?
Rotate a singly linked list to the right by `k` places. Each rotation moves the last element to the front.
## How it works
- Compute the length `n` of the list; make it circular (connect tail to head)
- Effective rotation: `k = k % n` (rotations of exactly `n` do nothing)
- The new tail is at position `n - k - 1` (0-indexed from head); the new head is its next
- Break the circle at the new tail: `new_tail.next = null`
## When to use
- Array/list rotation problems
- Cyclic shift operations on sequences
## Key Points
- O(n) time, O(1) space
- Always reduce `k` modulo `n` to avoid unnecessary full rotations
- Making the list circular and then cutting at the right point is cleaner than repeatedly moving the tail
