Classic problem, you'd think it's easy until you're staring at it live and second-guessing whether to do it iteratively or recursively.
Start by clarifying the problem constraints (e.g., iterative vs recursive, in-place, memory limits) and then walk through the standard iterative pointer manipulation approach. Explain the algorithm step-by-step, emphasizing how to avoid losing references, and analyze time and space complexity. If time permits, mention the recursive alternative and its trade-offs.
Pro tip: Demonstrate awareness of edge cases (empty list, single node) and discuss how to handle them gracefully. Also, mention that while recursion is elegant, it uses O(n) stack space, which might be a concern for very long lists—showing you consider practical constraints.
Ask if the list can be modified in-place, if recursion is allowed, and if there are memory constraints. Confirm the function signature and return type.
Decide between iterative and recursive solutions. The iterative approach is generally preferred for its O(1) space complexity and simplicity.
Describe using three pointers (prev, curr, next) to reverse the links one by one. Walk through a small example to illustrate.
State that time complexity is O(n) and space is O(1). Mention handling of empty list, single node, and ensuring the new head is returned.
Briefly mention the recursive approach (O(n) time, O(n) space) and when it might be appropriate, showing depth of knowledge.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.