Regression thinking

Regression thinking. After the fix, add the failing case to your mental suite and ask: what OTHER input would this same bug corrupt? A missing reset corrupts every multi-streak input, not just the one shown. That habit turns one bug into a family inspection — and on the exam, it double-checks your fix for free.

Reading broken code fast: the bug hides where the code looks too smooth. Real breaks are loud (<= next to a comment about "before the end"); compensations are quiet. Trace the failing example, and when your hand-drawn trace disagrees with the code's actual branches, you have found it. Never debug by re-reading without a concrete failing input on paper — the exam's debugging MCQs are exactly this skill at 90 seconds each.