Posts (238+)

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July 2026

Splay Trees:Move What You Touch to the Root

A splay tree is a BST that rotates the accessed node to the root. Recently used keys get cheap; amortized O(log n) without storing balance factors.

Algorithms

Binary Search:Cut the Space in Half When the Data Is Already Ordered

The sorted invariant, lower and upper bound, off-by-one, and what Arrays.binarySearch encodes when the key is missing.

Data Structures

LRU Cache:Hash Map Plus Doubly Linked List as One Machine

Least-recently-used eviction is O(1) only when a hash map points at nodes of a doubly linked list. How the two layouts share the work, and LinkedHashMap as the JDK shortcut.

Algorithms

Algorithms Roadmap:Pick the Procedure for the Job You Have

A map of search, sort, graphs, strings, DP, and systems algorithms — what job each one solves, when to skip it, and a living index of every post in this series.

Linux

Linux kill, pkill, and killall:Send Signals Safely

Hands-on kill, pkill, and killall recipes — choose SIGTERM, SIGKILL, or SIGHUP, target the right PIDs, and stop processes without wrecking managed services.

June 2026

Data Structures

Bloom Filters:Maybe-Yes, Definitely-No, and Why False Positives Are the Point

A Bloom filter is a bit array plus k hashes. It can say definitely not in the set, or maybe yes. False positives are the trade for tiny memory — never a false negative.

Java

Navigable Collections:TreeSet, TreeMap, and the Comparator Contract

Use TreeSet and TreeMap when keys must stay sorted — O(log n) red-black trees, Navigable ceiling/floor, and a Comparator that stays consistent with equals.

Data Structures

Skip Lists:Layers of Express Lanes Instead of Rotations

A skip list is a layered linked list where higher levels skip ahead. Expected O(log n) search without tree rotations — Redis and ConcurrentSkipListMap use this idea.

Java

PriorityQueue:Next-Best Without Sorting the Whole List

Use PriorityQueue when you need the next-best element in O(log n) — a heap, not a sorted list, and not a FIFO queue.

Linux

Linux lsof:See Who Is Using a File or Port

Hands-on lsof recipes for everyday work — find which processes hold files open, bind ports, or leak file descriptors.