Clarify the problem first: whether the arrays are sorted, if duplicates matter, and if the output should be symmetric or directional. Then propose an efficient solution using hash sets for O(n+m) time, and discuss trade-offs with sorting-based approaches.
Pro tip: At Meta, interviewers value clean, bug-free code and clear communication over clever tricks. Start by walking through a simple example to confirm your understanding, then optimize.
Ask about input constraints: sorted or unsorted, duplicates, expected output format (e.g., symmetric difference or elements only in first array).
Compare hash set (O(n+m) time, O(n+m) space) vs sorting (O(n log n + m log m) time, O(1) extra space). Mention trade-offs.
For hash set: build set from first array, iterate second to find elements not in set, and vice versa for symmetric difference. Handle duplicates if needed.
Write clean code with meaningful variable names. Test with edge cases: empty arrays, no common elements, all common elements, duplicates.
State time and space complexity. Discuss potential optimizations or alternative solutions if constraints change.
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