Free & beginner-friendly · bySrujan Chidarla

Learn DSA one stage at a time

A structured path from arrays to dynamic programming — hand-picked problems, a walkthrough video for nearly every one, and real interview tags. The progress numbers here are Srujan's, learning in public.

Start learning Practice schedule or follow Srujan's journal

curated problems: 159; curated problems
levels, easy → DP: 13; levels, easy → DP
video walkthroughs: 173+; video walkthroughs
companies in interview data: 419; companies in interview data

Step 0 · Learn the fundamentals

Pick one language and learn the syntax and built-ins you'll use in DSA before diving in.

How do you want to start?

Pick one. You can switch any time, and your progress counts everywhere.

A video for every problemEach problem in the schedule has a hand-checked walkthrough, mostly from NeetCode.Browse the schedule See who asks itInterview tags from real reports — Google, Amazon, Meta and hundreds more.Explore problems Spoiler-safe solutionsApproaches and code stay hidden until you have actually tried the problem.See an example Patterns cheatsheetTwo pointers, sliding window, BFS/DFS, DP — when to use each, with code.Open cheatsheet

Your problem of the day · #1

Thursday, Oct 15 · 0 of 159 solved

Two Sum

EasyArrays & Strings+8asked at Amazon, Google & more

Solve it Read Srujan's notes →

Watch after trying

Not solved yet? It stays here until you tick “I solved it”. Then go on to the next one right away, or come back tomorrow. Progress is saved on this device — sign in to keep it everywhere and get reminders.

Before you start · learn the topic

~10 minutes

Warm up for Two Sum: Arrays & Strings

Arrays and strings are the default input shape on LeetCode. If you can scan a list, count characters, and use a hash map for lookups, the later patterns feel much easier.

Make sure you know

→Index into a list and walk left → right
→Count frequencies with a hash map
→Use a set to check “have I seen this?”
→Build a new string or array from an answer

Static Arrays, Dynamic Arrays & StringsGreg Hogg · watch tonight

Tip: Say the brute force out loud first, then ask “what am I looking up twice?”

Today's problem: Two Sum · EasyGet this lesson as a reminder every evening →

Learning path

Stages to learn DSA

For anyone learning DSA: start with arrays and strings, then unlock easy patterns one at a time. Expand a stage for the why, what to learn, and starter problems — open one for its walkthrough, a step-by-step visual and the companies that ask it.

Every level, with your progress: the roadmap →