One Easy DSA Problem

Ask for a problem, not a label

“One Easy DSA Problem” does not identify an algorithm, input, or success condition. Ask for the exact question, examples, constraints, allowed mutation, and expected complexity. Restate the task in your own words so the interviewer can correct a misunderstanding early.

Then start with the simplest correct implementation and explain its cost. Use constraints to justify whether a hash map, two pointers, sort, BFS, stack, or simple scan is appropriate. Name one invariant that makes the optimized approach correct and walk through a representative example. Test empty input, one element, duplicates, ordering, numeric overflow, and invalid input only if the contract permits it. State time and auxiliary space in terms of the actual sizes rather than inventing bounds. This is stronger than guessing a memorized easy question, because it demonstrates professional problem framing and prevents solving the wrong task.

Complexity: For the confirmed easy DSA problem on n inputs, target O(n) time and O(1) auxiliary space unless a hash structure is essential.