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Foundations

Start here. How data sits in memory, and why that makes some operations instant and others slow.

7 lessons · 200 min

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Data in a row

Chains, piles and lines

Instant lookups

LessonHash Maps & SetsTurn a key into a bucket number and look there directly.35 minbeginner

Next pathCore Patterns →The handful of moves behind most array and string problems. Learn to spot which one a problem wants.