Permutations: Backtracking With Used Array
Solve Permutations with backtracking and a used array. Compare swap-in-place vs used-array, walkthrough, complexity, and interview tips.
·5 min read · #dsa#leetcode#backtracking
#intermediate
442 posts · page 7 of 10
Product of Array Except Self — Prefix and Suffix, No Division
Solve Product of Array Except Self in O(n) without division using prefix and suffix passes. Clean walkthrough plus interview script.
·5 min read · #dsa#leetcode#arrays
Reverse Linked List — Iterative and Recursive
Walk through Reverse Linked List with iterative pointer flipping and a clean recursive solution, plus complexity and interview talking points.
·5 min read · #dsa#leetcode#linked-list
Rotate Image — Transpose Plus Row Reverse
Rotate an n by n matrix 90 degrees in place by transposing and reversing each row. Walkthrough, edge cases, complexity, and interview script.
·4 min read · #dsa#leetcode#arrays
Search in Rotated Sorted Array: Modified Binary Search
Solve Search in Rotated Sorted Array in O(log n) with modified binary search. Pivot detection, half-decision logic, and interview talking points.
·5 min read · #dsa#leetcode#binary-search
Serialize and Deserialize Binary Tree — Preorder With Null Sentinels
The preorder-with-nulls encoding, the iterator-driven decoder, and why level-order is a worse choice than it looks.
·6 min read · #dsa#leetcode#trees
Sliding Window Maximum — Monotonic Deque Pattern
Solve Sliding Window Maximum in O(n) using a monotonic deque. Step-by-step walkthrough, interview script, and complexity analysis.
·5 min read · #dsa#leetcode#sliding-window
Spiral Matrix — Four-Boundary Walk Template
Solve Spiral Matrix with the four-boundary walk pattern. Clean implementation, edge cases for rectangles, complexity, and interview tips.
·5 min read · #dsa#leetcode#arrays
Subsets: The Backtracking Template Every Interview Tests
Generate all subsets of an array using backtracking and iterative bit-mask approaches. Includes complexity analysis and interview script.
·6 min read · #dsa#leetcode#backtracking
Top K Frequent Elements — Heap vs Bucket Sort
Solve Top K Frequent Elements with both a min-heap and a bucket sort approach. Trade-offs, complexity, and interview-ready walkthrough.
·5 min read · #dsa#leetcode#hashing
Trapping Rain Water — Two-Pointer in O(n)
Solve Trapping Rain Water in linear time and constant space using the two-pointer technique. Brute force, optimal walkthrough, and interview talk track.
·5 min read · #dsa#leetcode#two-pointers
Unique Paths: Grid DP and Math
Unique Paths in two ways — the O(m * n) grid DP that interviewers expect and the binomial-coefficient closed form that surprises them.
·5 min read · #dsa#leetcode#dp
Valid Anagram — Counting Characters in O(n)
A complete walkthrough of the Valid Anagram problem. Compare the sorting approach with the optimal hash map counting solution and learn how to explain it in interviews.
·6 min read · #dsa#leetcode#hashing
Valid Parentheses — The Classic Stack Pattern
A clean walkthrough of Valid Parentheses with the optimal stack solution. Covers edge cases, complexity, and how to explain the approach in interviews.
·6 min read · #dsa#leetcode#stack
Validate Binary Search Tree — Min/Max Bounds DFS
The seductive wrong answer, the correct min/max bounds approach, and how to defend it in an interview.
·5 min read · #dsa#leetcode#trees
Word Break: DP with a Word Dictionary
Solve Word Break with bottom-up dynamic programming. Includes brute force, edge cases, complexity analysis, and an interview script.
·6 min read · #dsa#leetcode#dynamic-programming
Word Ladder — BFS Over Wildcard-Pattern Buckets
The wildcard-pattern adjacency trick, why BFS is mandatory, and the bidirectional speedup.
·6 min read · #dsa#leetcode#graphs
Math for Coding Interviews: GCD, Primes, Modular Arithmetic
The essential math toolkit for interviews: Euclidean GCD, sieve of Eratosthenes, modular exponentiation, modular inverses, and common pitfalls.
·7 min read · #dsa#math#intermediate
Segment Tree: Range Queries and Updates
Learn segment trees for fast range sum, min, and max queries with point updates, including a clean iterative Python implementation.
·6 min read · #data-structures#segment-tree#intermediate
Topological Sort: Two Approaches Compared
Compare Kahn's BFS-based topological sort with DFS-based postorder, with Python implementations, complexity, and cycle detection.
·5 min read · #graphs#topological-sort#intermediate
Union-Find / Disjoint Set Union (DSU) Explained
Learn the union-find data structure with union by rank and path compression, why it runs in near-O(1) amortized, and how it powers Kruskal and islands.
·6 min read · #dsa#union-find#intermediate
Error Handling in Go: errors.Is, errors.As, and Wrapping
A practical guide to Go error handling: the error interface, sentinel values, custom types, wrapping with fmt.Errorf %w, and errors.Is and errors.As.
·5 min read · #go#errors#intermediate
Goroutines and Channels in Go: Concurrency Basics
Learn Go concurrency from the ground up: launching goroutines, communicating via channels, using select, range, and building a worker pool pattern.
·5 min read · #go#concurrency#intermediate
Go Packages and Modules with go.mod
A practical tour of Go packages and modules: go mod init, imports, internal packages, semantic versioning, and the replace directive for local development.
·5 min read · #go#modules#intermediate
Go Structs and Methods: Value vs Pointer Receivers
A clear guide to Go structs and methods: literal forms, defining methods, choosing value vs pointer receivers, and using embedding for composition.
·6 min read · #go#structs#intermediate
Java Collections Framework: List, Set, Map
Pick the right Java collection by performance and semantics. ArrayList vs LinkedList, HashMap vs TreeMap, immutability, and iteration without surprises.
·5 min read · #java#collections#intermediate
Java Inheritance and Polymorphism
Use extends, super, and method overriding without painting yourself into a corner. When to inherit, when to compose, and how sealed types help.
·5 min read · #java#oop#intermediate
Java Interfaces vs Abstract Classes
Choose between interfaces and abstract classes with confidence. Default methods, sealed interfaces, functional interfaces, and concrete decision rules.
·5 min read · #java#oop#intermediate
Java Streams and Lambdas: Functional Style on the JVM
Transform collections with lambdas and the Stream API. Map, filter, reduce, collectors, parallel streams, and the pitfalls of lazy pipelines.
·5 min read · #java#streams#intermediate
Helm Basics: Kubernetes Package Manager
Learn Helm fundamentals: helm install, charts, values.yaml, templating, releases, and when to choose Helm over plain Kubernetes YAML manifests.
·6 min read · #kubernetes#helm#intermediate
JavaScript Closures Explained with Real Examples
A practical guide to JavaScript closures, lexical scope, the classic loop bug, and the patterns that make closures genuinely useful in production code.
·7 min read · #javascript#closures#intermediate
DOM Manipulation in Vanilla JavaScript
A modern guide to vanilla DOM manipulation: query selectors, creating and inserting nodes, event handling, delegation, and when a framework is actually worth it.
·7 min read · #javascript#dom#intermediate
The JavaScript Event Loop: Microtasks vs Macrotasks
Build an accurate mental model of the JavaScript event loop, the call stack, web APIs, the task and microtask queues, and why setTimeout zero is not really zero.
·7 min read · #javascript#event-loop#intermediate
Using the Fetch API in JavaScript
A practical guide to the Fetch API: GET and POST requests, JSON, headers, error handling, AbortController, and the 4xx/5xx rejection gotcha that bites everyone.
·7 min read · #javascript#fetch#intermediate
JavaScript Prototypes and Prototype Inheritance
Understand the JavaScript prototype chain, how Object.create works, what class syntax desugars to, and why this still matters in modern code.
·7 min read · #javascript#prototypes#intermediate
JavaScript this and Function Binding
Demystify the JavaScript this keyword with clear rules, arrow vs normal functions, bind/call/apply, class methods, and the bugs that catch every developer.
·7 min read · #javascript#this#intermediate
Linux Cron Jobs and systemd Timers
Master scheduled tasks on Linux. Learn crontab syntax, fix common PATH and environment pitfalls, and use systemd timers as a modern alternative.
·6 min read · #linux#cron#intermediate
Linux Networking Commands: ip, ss, curl, dig
A practical guide to modern Linux networking tools. Learn ip, ss, curl, and dig to diagnose connectivity, inspect sockets, and resolve DNS issues fast.
·6 min read · #linux#networking#intermediate
Logistic Regression for Binary Classification
Learn how logistic regression turns a linear score into a probability, how to train it with scikit-learn, and how to evaluate binary classifiers using ROC-AUC.
·5 min read · #machine-learning#classification#intermediate
Using the Anthropic Claude SDK in Python
A practical tour of the Anthropic Python SDK: messages, streaming, tool use, prompt caching, and patterns for shipping Claude in production.
·4 min read · #anthropic#claude#intermediate
LangChain Basics in Python: Chains, Tools, and Memory
Learn LangChain by building real components in Python: prompt templates, chains, tool calling, and memory. Practical patterns you can ship today.
·4 min read · #langchain#python#intermediate
Generating Text Embeddings with an API
A practical tutorial on text embeddings: vector intuition, calling an embeddings API, choosing dimensions, computing cosine similarity, and caching the results.
·7 min read · #llms#embeddings#intermediate
Using the OpenAI Python SDK End-to-End
A working tour of the OpenAI Python SDK: chat completions, streaming, structured output, embeddings, tool calls, and production-grade error handling.
·4 min read · #openai#python#intermediate
Next.js Metadata API for SEO
Master the Next.js Metadata API with static and dynamic titles, OpenGraph tags, sitemaps, and robots.txt to ship pages that rank and share well.
·6 min read · #nextjs#seo#intermediate
pgvector: Add Vector Search to Postgres
Use pgvector to run embeddings, similarity search, and hybrid retrieval inside Postgres. Schemas, indexes, and a working Python pipeline.
·4 min read · #pgvector#postgres#intermediate
Pinecone Vector Database: Index, Upsert, Query
Build a working vector search pipeline with Pinecone in Python. Indexes, upserts, metadata filters, hybrid search, and patterns for production RAG.
·4 min read · #pinecone#vector-database#intermediate
asyncio Basics in Python
A practical introduction to Python asyncio: the event loop, async/await, asyncio.run, gather, create_task, and when to pick async over threads.
·6 min read · #python#asyncio#intermediate
Python Regex Basics with the re Module
A practical introduction to Python regex with the re module: match, search, findall, sub, groups, named groups, raw strings, and compiling patterns for speed.
·6 min read · #python#regex#intermediate