Inverted logic interview questions

Question 1

The "To do" tab shows the result of pendingTasks(). Users say it lists the tasks they already finished. Find the bug.

interface Task {
  id: string;
  title: string;
  done: boolean;
}

export function pendingTasks(tasks: Task[]): Task[] {
  return tasks.filter((task) => task.done);
}

Accepted Answer

Line 8: filter keeps the items for which the callback returns true, so this keeps the completed tasks. Pending tasks are the ones where done is false.

Question 2

validateUpload() should only accept PNG files. What does it actually allow?

var errNotPNG = errors.New("only .png files are allowed")

func validateUpload(filename string) error {
	if !strings.HasSuffix(strings.ToLower(filename), ".png") {
		return nil
	}
	return errNotPNG
}

Accepted Answer

Line 4: The condition is inverted: every file that is not a PNG passes validation, and real PNGs are rejected.

Question 3

This query feeds the "Top 10 players" leaderboard. Why is the leaderboard full of beginners?

SELECT player_id, MAX(score) AS best_score
FROM game_results
GROUP BY player_id
ORDER BY best_score ASC
LIMIT 10;

Accepted Answer

Line 4: ASC sorts from lowest to highest, so LIMIT 10 keeps the ten worst scores. A top-N query needs descending order.

Inverted logic: interview questions

How to spot it in code review

Why AI-generated code gets this wrong

Inverted logic: 3 practice questions

Pending tasks filter

Upload file-type check

Leaderboard top 10

Attempts distribution