The same-rank part was fine, group by rank, check count >= 3, done.
Clarify the problem constraints and edge cases, then propose an efficient algorithm that groups cards by suit and rank, sorts within groups, and extracts all valid runs and sets. Discuss time/space complexity and potential trade-offs between different approaches.
Pro tip: Explicitly state that you will output every contiguous sub-run of length >=3 within each maximal run, not just maximal runs, to show attention to detail. Also, mention that you will handle duplicate cards appropriately, as they can affect set formation.
Ask about input size, duplicate cards, card rank ordering (e.g., Ace high/low), and whether groups can overlap. Confirm that all contiguous sub-runs of length >=3 must be output.
Use a hash map to group cards by suit and another to group by rank. For each suit, store ranks in a sorted set or list; for each rank, store the count of cards.
For each suit, sort the ranks and scan for consecutive sequences. For each maximal run of length L >=3, generate all contiguous sub-runs of length >=3. For each rank with count >=3, output the set (if duplicates allowed, decide whether to output one set or multiple).
Discuss time complexity: O(N log N) due to sorting within suits, where N is number of cards. Space complexity: O(N) for storing groups. Consider if sorting can be avoided using counting sort if ranks are bounded.
Walk through a small example, such as ['3H','4H','5H','6H','7S','7D','7C'], to demonstrate output: runs of hearts (3-4-5, 4-5-6, 5-6-7, 3-4-5-6, 4-5-6-7, 3-4-5-6-7) and set of sevens.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.