My first instinct was to just slice and concatenate which works fine but uses extra space.
Start by clarifying the problem constraints (e.g., k can be larger than array length, in-place modification expected) and discussing a simple approach like using an extra array or reversing. Then, for the follow-up, explain the reversal algorithm: reverse the entire array, then reverse the first k elements, then reverse the remaining n-k elements. This achieves O(1) extra space and O(n) time.
Pro tip: Mention that you can optimize by taking k modulo n to handle cases where k > n, and note that the reversal method is optimal for space and time. Also, be prepared to discuss trade-offs between different approaches (e.g., using cyclic replacements vs. reversal) in terms of code complexity and constant factors.
Ask about input size, whether k can be negative or larger than array length, and if in-place modification is required. Confirm that O(1) extra space is desired for the follow-up.
Mention simple solutions like creating a new array or rotating one step at a time (O(n*k) time). Explain their time/space complexities and why they might not be optimal.
Explain the three-step reversal: reverse the whole array, then reverse the first k elements, then reverse the last n-k elements. Show that this yields the rotated array.
State that time complexity is O(n) and space is O(1). Handle edge cases: k=0, k=n, k>n (use k % n), empty array, and single-element array.
Mention cyclic replacements (juggling algorithm) as another O(1) space method, and compare its trade-offs (e.g., more complex to implement, potential for infinite loops if not careful).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.