LeetCode Patterns by Sean Prashad

What it is

Sean Prashad built LeetCode Patterns in 2019 as a free and open-source way to practise by pattern rather than at random. The repository on GitHub has about 13,900 stars as of September 2026 and was updated in September 2026 (the site was recently rebuilt with Next.js).

The site lists 179 LeetCode questions (41 easy, 112 medium and 26 hard in the current data), grouped under patterns such as arrays and hashing, two pointers, sliding window, trees, graphs, heaps, intervals, dynamic programming and bit manipulation. A handful (13) need LeetCode Premium. The acknowledgements credit the Blind 75 list, Grokking the Coding Interview and the "14 Patterns to Ace Any Coding Interview Question" article as inspiration.

Features

• Filters by pattern, company and difficulty, plus search and a shuffle mode.
• Company data for each question, showing which companies are known to ask it.
• Progress tracking stored in your browser, with optional sign-in to sync across devices.
• Notes, stars and review dates, so you can mark problems to revisit and see which are due for review.
• Roadmaps: a beginner roadmap in phases (arrays and hash tables, two pointers, sliding window, linked lists, binary search, trees, sorting and intervals, graphs, heaps, matrix traversal, prefix sums) and an experienced-candidate order by topic.
• Helpful tips: a table of heuristics that suggests possible approaches based on the problem's constraints.

Why it is worth bookmarking

It is the fastest tool for one question: what should I practise next? No course, no upsell. Pick a weak pattern, filter, work the list. The beginner roadmap's guidance is sensible: spend no more than about 30 minutes before studying the solution, study it until you can explain it to someone else, expect to struggle for the first month, and do not memorise solutions.

Before you start

The README recommends knowing the main data structures (arrays, maps, linked lists, queues, heaps, stacks, trees and graphs) and common algorithms (BFS, DFS, binary search and recursion) first. Without them, start with a data structures course.

How to use it well

• Beginners: follow the beginner roadmap phase by phase.
• Experienced: filter by your weakest patterns and do all mediums in them.
• Near an interview: filter by the target company for a final pass, but do not rely on company tags alone.
• Use the review dates to redo problems a week or two later.
• Pair it with explanations from NeetCode videos or LeetCode editorials when stuck. Java solutions are in the repository's solutions branch.

Best for: anyone already practising who wants a pattern-based index and a clear next problem.