Blog

N-Queens separates candidates who know backtracking from those who understand constraint propagation. The O(1) diagonal check using sets is what interviewers want to see.

The duplicate-skip pattern is what separates Combination Sum I from II. Master sort + skip, in-place grid marking for Word Search, and why `i > start` matters.

Build a spec-compliant Promise from scratch in 75 lines of JavaScript. Understand state machines, microtask scheduling, thenable resolution, and why .then(s,e) and .then(s).catch(e) aren't the same.

BST problems aren't just binary tree problems — the sorted-order property changes everything. Master validate, kth smallest, and the iterator pattern that shows up in real interviews.

React Context is great for static config but a footgun for dynamic state. Learn how to split contexts by update frequency and separate state from dispatch.

Three linked list problems, one underlying playbook: dummy heads, divide-and-conquer merging, and the find-middle/reverse/interleave pipeline that makes LC 143 tractable.

One BFS template, three interview problems. Level-order, zigzag traversal, and right side view all reduce to the same queue loop with a small variation each time.

Post-order DFS, the global-state side-effect trick, and nested tree matching — four problems that teach you everything about recursive tree traversal in JavaScript.

Learn how React.lazy, Suspense boundaries, and React 19 concurrent features (useTransition, useDeferredValue) eliminate bundle bloat and loading jank.