Roadmap

145 lessons, 6 phases, one order. Each module unlocks nothing — you can start anywhere — but this is the sequence that needs the least backtracking.

Foundations

Cost, then the one structure everything else is built on. Nothing here is optional.

0 / 26 lessons

Big-O
You are here
Read growth curves at a glance instead of memorising a table.
5 lessons · 22 min0 / 5
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Arrays
Pointers, windows and in-place tricks, drawn out step by step.
8 lessons · 40 min0 / 8
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Searching
Watch a search space collapse until only the answer is left.
5 lessons · 26 min0 / 5
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Sorting
See why the clever sorts beat the obvious ones.
8 lessons · 39 min0 / 8
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Six shapes for holding data, and the trade each one makes to be fast at something.

0 / 36 lessons

Linked Lists
Follow the pointers — and learn every trick they hide.
6 lessons · 28 min0 / 6
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Stacks & Queues
Two humble rules, LIFO and FIFO, doing surprisingly heavy lifting.
5 lessons · 24 min0 / 5
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Hash Tables
Trade a bit of memory for answers in constant time.
5 lessons · 23 min0 / 5
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Trees & BST
Hierarchies, ordered searches, and the paths between nodes.
8 lessons · 40 min0 / 8
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Heaps
Keep the most important thing on top — without sorting the rest.
4 lessons · 22 min0 / 4
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Graphs
Nodes, edges, and the searches that ripple across them.
8 lessons · 44 min0 / 8
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Recursion, then recursion with a memo. The half of the interview that is pure technique.

0 / 15 lessons

Recursion
Watch the call stack grow, shrink, and finally make sense.
5 lessons · 27 min0 / 5
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Dynamic Programming
Solve every subproblem once, then let the table do the work.
10 lessons · 55 min0 / 10
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What happens once one machine is not enough — and once one thread is not either.

0 / 35 lessons

System Design
Scale, cache, shard — and know what each choice costs you.
15 lessons · 81 min0 / 15
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Concurrency
Threads, locks and races — watch the interleavings that bite.
10 lessons · 46 min0 / 10
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SQL
Queries you can watch run — joins, groups, indexes, transactions.
10 lessons · 50 min0 / 10
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The two rounds that are not about algorithms: object design, and telling a true story well.

0 / 18 lessons

Low-Level Design
Objects, interfaces and patterns that survive the follow-up question.
10 lessons · 49 min0 / 10
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Behavioral
Tell true stories that carry signal — and skip the traps.
8 lessons · 37 min0 / 8
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Embeddings, retrieval, evaluation, agents — the round that did not exist five years ago.

0 / 15 lessons

AI & ML
From embeddings to agents — see how modern AI actually works.
15 lessons · 72 min0 / 15
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