Classic problem but I still fumbled the dedup logic under pressure.
Start by clarifying the problem constraints (e.g., input size, duplicates, sorted or not) and then propose an efficient solution. The optimal approach is to sort the array and use a two-pointer technique for each element to find pairs that sum to its negation, ensuring O(n^2) time and O(1) extra space (excluding output).
Pro tip: Mention that you would handle duplicates carefully to avoid duplicate triplets, and discuss trade-offs between sorting vs. using a hash set. Also, relate the problem to real-world ML scenarios like feature engineering or similarity search to show practical insight.
Ask about input size, whether the array can contain duplicates, if the output should be sorted, and if there are memory constraints. This shows attention to detail and helps tailor the solution.
Acknowledge that a triple nested loop (O(n^3)) is straightforward but inefficient for large n. This sets the stage for optimizing.
Sort the array, then iterate through each element as the first number of the triplet. For each, use two pointers (left and right) to find pairs that sum to the negative of the current element, skipping duplicates to avoid repeated triplets.
State time complexity O(n^2) and space O(1) (or O(n) if considering sorting). Discuss edge cases: empty array, less than 3 elements, all zeros, large duplicates, etc.
Walk through a small example (e.g., [-1,0,1,2,-1,-4]) to demonstrate correctness. If coding, write clean code with comments and handle duplicates properly.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.