I shut down the L train in a graph: max flow, min cut and AI agents on the New York subway
Picture 8 a.m. on a Wednesday in October. A signal fire in the Canarsie Tube stops the L between Bedford Av and 8 Av, in both directions, until furt…
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Engineering a Multimodal Travel Planner on a 228,060-Edge Graph
A flight search engine answers a well-defined question: which available flights connect two airports? A door-to-door travel planner must answer a mo…
Cube translates in non-abelian groups: what commutativity is worth
This is from MV2's open notebook on Kakeya-type problems ( https://github.com/munimtechnologies/kakeya-small-fields ). An earlier post showed that a…
2Sum in Constant Time?
Is it possible to solve the two_sum problem in constant time O(1) , I asked myself. Reading through Mr Wengrow's DSA book, I soon come to find out t…
Why your topological sort gives a different answer on every run
You have a few tasks, and some of them depend on others. You put them in a graph, sort it topologically, and print the order. Then you run the progr…
Can Algorithms Track Behaviour? Monitoring Coordinated Online Actions
Online action detection is central to modern cybersecurity analysis. Simply tracking individual accounts provides only scattered data points; it doe…
Let the player build the maze - a 576-cell flow field for a tower defense map
Most tower defense maps give enemies a fixed lane. In one map of Void Parry 's tower-defense mode, "Null Grid", there is no lane at all: an open 32x…
How Uber Computes Estimated Time of Arrival (ETA)
Short answer: how does Uber compute ETA? Uber snaps noisy GPS pings to the road network (map matching), finds candidate routes on a road graph, and…
2026 - Backend Interview Questions
1. Core Java & OOP Write an immutable class in Java Comparable vs Comparator with examples What is a Functional Interface? Can it have default a…
How a Word file becomes a printed book: line breaks, widows and the KDP gutter
Originally published at getnobody.org . A Word document has no pages, not really. It has paragraphs, and Word decides where the pages fall while you…
Mastering Two Pointers: A Step-by-Step Guide to Solving Sequence Problems
Mastering Two Pointers: A Step-by-Step Guide to Solving Sequence Problems Two Pointers is an algorithmic pattern used to solve problems by tracking…
Five results: I spent time proving splines don't help trajectory databases
If you work with GPS tracks, this idea shows up sooner or later: why store a trajectory as a polyline of thousands of points when a vehicle moves sm…
600 Terms, a Degree-14 Rational Generating Function, and a Limit Near π
I have been working on a deterministic operator called (EOA). It maps the spoken names of letters into integer sequences. For one English encoding,…
Building a Zero-Lag Client-Side Python Visualizer with Pyodide & WebAssembly
Understanding code execution, call stacks, and pointer mutations can be tricky—especially when debugging complex algorithms, recursion, or data stru…
LeetCode 4000 - 4010 problems: patterns and approaches explained
LeetCode has started publishing problems numbered 4000 and above. At the time of writing this post, there are already 4055 problems. In this post, I…
Bayan Flow 0.5.0: Tree Traversals, Graph Algorithms, and Turning a Visualizer Into a Platform
Version 0.5.0 of Bayan Flow just shipped, and it's the biggest one so far. I'd promised tree traversals and graph algorithms a while back. They're f…
Merge Sort : Sorting in O(n log n) Using Divide and Conquer
Why should you care? Sorting is one of the most common problems in programming. You may need to sort: Student marks Product prices Names Search resu…
My AI Content Got Flagged as Templated. The Fix Was N-gram Math.
Google doesn't read your articles. It fingerprints them. Earlier this year, a batch of comparison articles across my B2B sites got hit with the quie…
HLD: Twitter / X
Design a social media platform where users post tweets, follow each other, and see a timeline of tweets from accounts they follow. 1️⃣ Clarify Requi…
How Does Ground Moving Target Indication Work? A Developer’s Guide to GMTI Processing
How Does Ground Moving Target Indication Work? Ground Moving Target Indication, or GMTI, is a radar processing capability used to detect moving obje…
Building a TypeScript Code Radar: What an AST Reveals That Text Search Misses
Today I started experimenting with Tree-sitter . I had heard the name before, but I had never actually used it. My goal was simple: take a TypeScrip…
Functions Behind the Scenes
Why should you care? You use functions constantly: int result = add ( 10 , 20 ); It looks simple. You call a function, it does some work, and it ret…
Designing Algorithms That Adapt to Their Input Distribution
Most algorithms are taught as if the input were some abstract thing that simply arrives at the function boundary. An array appears. A graph appears.…
Why Fixed-Window Rate Limiters Fail (And How to Fix Them with Math)
If you’ve ever built an Express API, you’ve probably reached for standard rate-limiting middleware to protect your login or payment endpoints from D…
Building a Location-Aware Discovery Engine: Why “Nearby” Isn't Just Distance
"Nearby" sounds like a simple feature. Calculate the distance between the user and every location. Sort by distance. Done. In practice, that's not e…
An O(1) Space Alternative to "Rearrange Array Alternately" Using Sequential Suffix Reversal
If you've spent time on LeetCode or GeeksforGeeks, you've probably run into the classic "Rearrange Array Alternately" problem. The premise: given a…
How We Made Image Copy-Detection ~1,000,000 Faster — by Refusing to Look at Pixels
Structural hashing for pixel art: a 1024-byte key that answers 'is this the same artwork?' in 115 nanoseconds — and then tells you exactly what was…
Optimizing LLM Context for OpenAPI: A Deterministic Approach to Token Reduction
How deterministic context batching reduced approximate token usage by ~81.7% while building an agentic API testing prototype See It in Action I also…
Guillotine Cutting vs Free Nesting for Rectangular Parts
The most space-efficient sheet layout is not always the easiest one to cut. The right method depends on the machine, material, and value of workshop…
How We Evolved a Cultural Recommendation Feed From a Weighted SQL Ranker to a Narrative Affinity Model
Building a personalization engine for a multi-format content feed, without machine learning, and the testing process that forced us to rebuild it. T…