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Foundations: Complexity & Core Structures

Big-O intuition, the core data structures, and the pattern-recognition mindset everything else builds on.

0 of 6 lessons complete · 76 min total

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  1. Big-O in Plain EnglishWhat time and space complexity actually mean, the common classes (O(1) to O(2^n)), and how to state complexity unprompted the way mid-level interviews expect.Lesson · 15 minNot completed
  2. The Complexity RaceSee why algorithm choice matters more than hardware.Animation · 9 minNot completed
  3. Core Data Structures TourArrays, dynamic arrays, strings, hash maps/sets, stacks, queues/deques, linked lists, trees, heaps, tries, and graphs — what each is good at and its operation costs.Lesson · 18 minNot completed
  4. Divide & Conquer and Merge SortThe split-solve-merge idea behind merge sort, quickselect, and tree construction.Animation · 10 minNot completed
  5. The Pattern Map: Reading Problem SignalsThe master decision flowchart: signal words like 'sorted', 'shortest', 'all combinations', or 'top k' and which pattern each one points to. Pattern recognition is the real interview skill.Lesson · 16 minNot completed
  6. Foundations CheckpointComplexity classes, structure operation costs, and matching signal words to patterns.Checkpoint · 8 minNot completed