Start by clarifying the problem and edge cases, then propose a solution using a hash map to map original nodes to their copies, which handles both next and random pointers in O(n) time and space. Alternatively, present the O(1) space interleaving approach if the interviewer wants optimization. Walk through the code and test with a small example.
Pro tip: Mention that the hash map approach is straightforward but uses O(n) extra space, and then offer the interleaving method as an optimization to show depth. This demonstrates you can balance clarity and efficiency.
Ask if the list can be empty, if random pointers can be null, and if nodes can point to themselves. Confirm that deep copy means new nodes with same values and pointer structure.
Decide between hash map (O(n) space) and interleaving (O(1) space). Start with the hash map for simplicity, then mention the optimized approach if time permits.
For hash map: first pass create copy of each node and store mapping; second pass set next and random pointers using the map. For interleaving: insert copy after each original, set random pointers, then separate lists.
Walk through a small list (e.g., 2-3 nodes) with random pointers, including edge cases like null random pointers. Verify the copy is independent.
State time and space complexity: O(n) time for both approaches; O(n) space for hash map, O(1) space for interleaving (excluding output).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.