CS foundations · CodeWiki

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01 · Algorithms

3 topics

Algorithmic complexity Estimate time and space growth with asymptotic notation and choose implementations that scale for real inputs. beginner 18 min Recursion Define recursive cases, prove termination, trace the call stack, and replace recursion when depth is unsafe. intermediate 17 min Sorting and searching Choose and implement sorting and searching strategies from data shape, ordering guarantees, and complexity. beginner 17 min

02 · Data structures

3 topics

Arrays and linked lists Choose between contiguous arrays and linked nodes by access patterns, mutation costs, locality, and memory overhead. beginner 18 min Hash maps Use hashing, collision handling, resizing, and key equality to build and evaluate constant-time lookup tables. intermediate 17 min Trees and graphs Model hierarchical and connected data, then traverse it with depth-first and breadth-first strategies. intermediate 17 min

03 · Networking

6 topics

DNS resolution Trace names through recursive and authoritative DNS, caching, record types, TTLs, and failure modes. intermediate 15 min HTTP semantics Design and diagnose HTTP exchanges using methods, status codes, fields, caching, idempotency, and connection boundaries. beginner 20 min HTTP/2 HTTP/2 carries concurrent requests over one connection with binary frames, multiplexing, and HPACK; learn its streams, flow control, and failure boundaries. intermediate 16 min Network programming Start with socket, TCP, and UDP semantics, then handle framing, timeouts, shutdown, and backpressure without ambiguous boundaries. intermediate 16 min TLS connections Verify how certificates, hostnames, trust chains, handshakes, and key agreement protect connections. intermediate 16 min WebSocket WebSocket carries two-way messages on one connection; learn its handshake, boundaries, closing, recovery, security, and backpressure. intermediate 16 min

04 · Operating systems

3 topics

Linux Understand Linux kernel boundaries, files and permissions, processes, descriptors, and signals, then troubleshoot them with verifiable commands. intermediate 20 min Processes and threads Distinguish processes and threads, trace their lifecycle and shared state, and reason about scheduling and synchronization. intermediate 17 min Virtual memory Reason about address spaces, pages, allocation, caching, swapping, and memory faults in running programs. intermediate 20 min

05 · Git and shell

3 topics

Git's internal model Understand Git through objects, references, the index, and the commit graph, then rebase, undo, and recover work safely. intermediate 17 min Pipes and redirection Compose commands with standard streams, pipelines, redirection, and exit handling without losing errors or data. intermediate 16 min Shell basics Navigate files, quote arguments, expand variables, inspect exit status, and run commands safely in a shell. beginner 22 min

06 · Text and numbers

5 topics

Dates and time Model instants, civil time, time zones, durations, and calendar arithmetic without hiding context in ambiguous conversions. intermediate 17 min Floating-point arithmetic Predict representation error, rounding, overflow, and reliable comparisons in binary floating-point calculations. intermediate 18 min Internationalization Internationalization makes locale, time zone, plural rules, and writing direction explicit inputs so one product can serve different regions correctly. intermediate 21 min Regular expressions Build, read, test, and constrain regular expressions for reliable validation, search, capture, and replacement while avoiding escape and performance traps. beginner 16 min Unicode text Handle code points, encodings, grapheme clusters, normalization, and text comparison without corrupting user data. intermediate 18 min