The O(n) Club: Counting Squares in Binary Matrices (Because Rectangles Are for Quitters)
The O(n) Club: Counting Squares in Binary Matrices (Because Rectangles Are for Quitters) ⚡ TL;DR Counting all squares (not just the “big…
The O(n) Club: Subarray Minimums & The Stack That Outsmarts Brute Force
The O(n) Club: Subarray Minimums & The Stack That Outsmarts Brute Force ⚡ TL;DR Want to sum up the minimum of every contiguous subarray?…
The Mutex Club: AtomicBoolean — The Lock-Free Flag Guardian
Ever wished a boolean could guard a castle without all that lock-and-key fuss? Meet AtomicBoolean, Java’s hardware-accelerated sentry that…
The Mutex Club: AtomicReference’s Double-Edged Sword
Key Insights ### Lock-Free Algorithms AtomicReference is the secret sauce behind many lock-free data structures: no JVM locks, no thread…
The O(n) Club: Delete and Earn – When House Robber Goes Full Arcade
The O(n) Club: Delete and Earn – When House Robber Goes Full Arcade ⚡ TL;DR Every time you delete a number, you also assassinate its…
The O(n) Club: Detecting 132 Patterns Faster Than Your Interviewer Can Blink
The O(n) Club: Detecting 132 Patterns Faster Than Your Interviewer Can Blink ⚡ TL;DR Find three numbers in an array that say, “Look, I zigged…
The Mutex Club: Mastering AtomicInteger in Java Concurrency
Foundation: Why AtomicInteger? If you’ve ever seen your Java app freeze under thread contention, you know that synchronized blocks are…
The Mutex Club: The Volatile Keyword – Hero, Hazard, or Just a Wingman?
Introduction Volatile… hero or hazard? Think of it as your underpaid sous-chef that always brings you the latest ingredients (visibility), but…
The O(n) Club: Pacific Atlantic Water Flow’s Reverse-DFS Party Trick
The O(n) Club: Pacific Atlantic Water Flow’s Reverse-DFS Party Trick ⚡ TL;DR Which cells in a height matrix can get their water to both…
The O(n) Club: Largest Divisible Subset: DP, Java, and Chaos Prevention
The O(n) Club: Largest Divisible Subset—DP, Java, and Chaos Prevention ⚡ TL;DR This problem is basically “who can divide whom at the nerd…