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Find why your binary search hangs, without the fix

Practice: Setting limits and rules. About 5 minutes.

About this exercise

Your binary search for an algorithms side project sometimes never returns. You want to fix it yourself, so ask for exactly 3 numbered lines labeled 'Bug: line N - ...', 'Hangs on: find([...], x) - ...' with a concrete call that really loops forever, and 'Hint: ...', each under 20 words. No code blocks, no corrected line, under 75 words.

Common mistakes when you ask AI for this

  • Getting the fix. The AI hands you lo = mid + 1 and a rewritten function, so you never trace it yourself. Try: Say: "Don't give the corrected line or code. Clues only."
  • Blaming the wrong line. Your note points at line 9, and the AI may follow your guess. Try: Ask: "Which line causes the hang? Label it 'Bug: line N'."
  • No input to trace. Without a small failing call, you can't see the loop get stuck. Try: Add: "Give a concrete call that hangs, labeled 'Hangs on:'."
  • A long lesson. The AI explains binary search from the start. Try: Add: "Exactly 3 numbered lines, each under 20 words."

What a strong prompt includes

  • Asks for clues, not the fix
  • Gives the labels
  • Asks for a failing input
  • Sets the number of lines
  • Caps each line

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