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Courses

22 courses, 884 lessons, 4521 exercises, across three subjects. Algorithms runs in order, each course assuming the one before it. AI Coding is a second ladder, about working with AI rather than about algorithms. System Design is a third, about the systems behind the code. All three share one engine and one daily session, and 13 of the courses are free here with an account, the first in every subject included. The practice tracks are company problems you can take in any order, and they are part of AlgoFox Pro.

Algorithms courses

Data structures and algorithms, 6 courses from beginner to advanced. Start at DSA Foundations if you are not sure.

  1. 1

    DSA Foundations

    Build your foundations: arrays, hashing, linked lists, stacks & queues, recursion, and trees — the data structures every interview builds on.

    Islands
    5
    Lessons
    44
    Exercises
    275
    Free on web
  2. 2

    Array Patterns

    Master the array patterns interviews love: two pointers, sliding window, prefix sums, intervals, and matrix tricks.

    Islands
    5
    Lessons
    45
    Exercises
    282
    EasyPro
  3. 3

    Search & Priority Patterns

    Find answers faster: binary search, searching the answer space, heaps for top-K, and monotonic stacks.

    Islands
    4
    Lessons
    35
    Exercises
    215
    IntermediatePro
  4. 4

    Trees & Graphs

    Traverse everything connected: tree DFS and BFS, grid flood fill, graph fundamentals, topological order, shortest paths, and tries.

    Islands
    7
    Lessons
    63
    Exercises
    398
    IntermediatePro
  5. 5

    Backtracking & Greedy

    Explore decision trees with undo, prune dead branches early, and learn when one locally best choice is provably enough.

    Islands
    4
    Lessons
    36
    Exercises
    229
    AdvancedPro
  6. 6

    Dynamic Programming

    Turn exponential brute force into linear tables: overlapping subproblems, memoization, tabulation, and the classic 1D, grid, sequence, and scheduling patterns.

    Islands
    5
    Lessons
    45
    Exercises
    280
    ExpertPro

AI Coding courses

A second ladder, from what generative AI is to building, guarding and running it. Short lessons built on judgement calls: which tool, which prompt, which claim to check, which action needs a person. No model trivia. Claude Code in Practice and Agent Harnesses in Practice are tool guides.

  1. 1

    AI Foundations

    What generative AI is and is not, and when to trust what it says: the two islands every other AI course assumes.

    Islands
    2
    Lessons
    12
    Exercises
    71
    BeginnerFree on web
  2. 2

    AI-Assisted Coding

    Direct a coding assistant or agent through a real codebase: set its permissions, specify the work, generate, debug, test, review, and stay the owner of the code.

    Islands
    6
    Lessons
    37
    Exercises
    212
    EasyFree on web
  3. 3

    Working With AI Tools

    Optional, for work outside a codebase: choose the tool, give it context, prompt well, and use it responsibly.

    Islands
    4
    Lessons
    25
    Exercises
    142
    EasyFree on web
  4. 4

    Building AI Applications

    Put a model behind a product: the request and its parameters, structured outputs and function calling, retrieval, and the cost, latency and privacy decisions that ship.

    Islands
    4
    Lessons
    25
    Exercises
    143
    IntermediateFree on web
  5. 5

    Agents and Reliability

    Build agents that stop, stay inside their permissions, survive prompt injection, and prove it with evals and traces.

    Islands
    4
    Lessons
    23
    Exercises
    133
    AdvancedFree on web
  6. 6

    Deep AI Engineering

    What is under the assistant: tokens, attention and training on one side, decoding, caches, throughput and quantization on the other, for the engineer who has to explain a failure or size a deployment.

    Islands
    2
    Lessons
    13
    Exercises
    74
    ExpertFree on web
  7. 7

    Claude Code in Practice

    A tool guide: sessions and modes, the CLAUDE.md memory files and when each loads, plan mode and the working loop, skills and subagents, and the permissions, hooks and MCP settings that keep a team's setup safe.

    Islands
    5
    Lessons
    32
    Exercises
    180
    EasyFree on web
  8. 8

    Agent Harnesses in Practice

    A tool guide across six products: what a harness adds to a stateless model, how OpenClaw, Hermes, OpenCode, Oh My Pi, OpenRouter and Herdr each handle memory, skills, tools, routing and triggers, and how to choose one and lock it down.

    Islands
    6
    Lessons
    34
    Exercises
    194
    IntermediateFree on web

System Design courses

A third ladder, about the systems behind the code: frame the requirements, size the load, write the contract and the data model, then carry one design through a spike and a failure to a tradeoff you can defend with a number. Every question states the constraint that makes one answer best.

  1. 1

    System Design Foundations

    Frame a system before you draw it: the requirements that matter, the numbers behind them, the API and data model that hold up, and one design carried through a spike and a failure to a tradeoff you can defend.

    Islands
    6
    Lessons
    36
    Exercises
    209
    EasyFree on web
  2. 2

    Building Scalable Services

    Make a service fast under load and keep it that way: caches and their invalidation, queues and the workers behind them, partitions and the key that spreads the load, fan-out, and search.

    Islands
    4
    Lessons
    24
    Exercises
    140
    IntermediateFree on web
  3. 3

    Distributed Reliability

    Keep a system correct when parts of it fail: replication and the consistency it can promise, coordination and leases, transactions across services, and the recovery that gets the data back.

    Islands
    4
    Lessons
    24
    Exercises
    140
    AdvancedFree on web
  4. 4

    System Design Case Studies

    Whole systems, end to end: a social feed, a chat service, a payment ledger, a video platform and a search engine, each carried from the ask through its numbers, its hard part and its failure to a design you can defend.

    Islands
    5
    Lessons
    25
    Exercises
    145
    ExpertFree on web

Practice tracks

Problems these companies are known to ask, taken apart step by step. AlgoFox is not affiliated with, endorsed by, or sponsored by any of them; the names describe what the track covers.

  • Amazon Coding Interview

    Amazon's greatest hits: hashing, two pointers, grids, and binary search on the answer.

    Islands
    10
    Lessons
    90
    Exercises
    311
    IntermediatePro

  • Google Coding Interview

    Google's angle: arrays and strings done exactly right, one careful step at a time.

    Islands
    8
    Lessons
    72
    Exercises
    250
    IntermediatePro

  • Meta Coding Interview

    Meta's fast set: stacks and parentheses, top-K, prefix products, and sliding windows.

    Islands
    8
    Lessons
    72
    Exercises
    249
    IntermediatePro

  • Apple Coding Interview

    Apple's staples: intervals, an LRU cache, prefix sums, and rebuilding trees from traversals.

    Islands
    8
    Lessons
    72
    Exercises
    249
    IntermediatePro

Every course practises the same typed interactions. There is no code editor and nothing to run.

Multiple choiceTraceComplete codeCode orderDebugShort answer