← Bytedance Interview Insights
I knew the no-duplicates version cold, so my first instinct was to just write that and slap a set on the output.
Sort the array to group duplicates, then use backtracking to generate subsets while skipping duplicate elements at the same recursion level. Alternatively, use an iterative approach that builds subsets and avoids duplicates by only adding new elements if they differ from the previous element. Emphasize the importance of handling duplicates to ensure unique subsets.
Pro tip: Mention that sorting is crucial for efficient duplicate skipping, and clarify that duplicates are skipped only at the same decision level to avoid missing valid subsets. Also, discuss time complexity: O(2^n) subsets, but with duplicates, the actual number is less.
Confirm that the output should contain unique subsets and that order doesn't matter. Sort the input array to bring duplicates together.
Decide between backtracking (DFS) or iterative bitmask. Backtracking is more intuitive for handling duplicates.
At each recursion level, iterate through elements, skip if the current element equals the previous and the previous was not used in this branch. Add the current subset to the result at each step.
Explain that the number of subsets is at most 2^n, and with duplicates, it's less. Time complexity is O(2^n) and space O(n) for recursion stack.
Test with empty array, all duplicates, and mixed duplicates to ensure correctness.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.