Classic problem but the random pointer is what trips people up.
Start by clarifying the problem and edge cases, then propose a solution using a hash map to map original nodes to their copies, allowing you to set next and random pointers in a second pass. Alternatively, present the O(1) space interleaving approach if asked for optimization, and analyze time/space complexity.
Pro tip: Mention the trade-off between the hash map approach (simpler, O(n) space) and the interleaving approach (O(1) space but modifies the original list temporarily). This shows you understand both clarity and optimization, which Meta values.
Ask about constraints: can the list be empty? Can random pointers be null? Is modifying the original list allowed? Confirm that deep copy means new nodes with same values and pointer structure.
Decide between hash map (two-pass) and interleaving (three-pass). Explain the trade-offs in time and space complexity, and pick one based on constraints or interviewer preference.
For hash map: first pass create copy nodes and map originals to copies; second pass set next and random pointers using the map. For interleaving: insert copy nodes after originals, set random pointers, then separate the lists.
State time complexity O(n) and space complexity (O(n) for hash map, O(1) for interleaving). Walk through a small example, including edge cases like empty list, single node, and random pointers to null.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.