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📜 WAYPOINT LESSON

Checkpoint: symmetry

⭐⭐⭐ advanced⏳ 15 min read📍 Lesson 188 of 256

Pairwise comparison checkpoint: compare each pair once, fail fast.

Symmetry is the purest 2D-indices exercise: every element must meet its mirror, each pair checked exactly once, and the first mismatch ends the scan. Compare against your instinct to check every cell twice (harmless) or only the upper triangle against the wrong index (fatal).