DSA Master ReferenceZero to Hero for Senior/Staff Interviews

Patterns · Invariants · Problems — Java 17, Grokking-style depth, Instant offline reference — 340 pages, searchable PDF

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Sliding Window on 9 cells with two overlapping windows

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21 Core Patterns

Every pattern with story intro, when-to-use, templates, canonical problems, and interview scripts. Sliding Window to Quickselect.

Explore patterns

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Learning Notes on Every Line

Why Long.MIN_VALUE? Why right >= k-1? Every non-obvious code decision explained bullet-by-bullet.

See in action

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8-Week Roadmap

Pre-flight quiz, weekly cadence (2 canonical + 2 variations + 1 mock), staff-level readiness signals.

See the plan

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205 Interactive Problems

Every problem has a Java runner (CheerpJ WASM), progressive hints, company tags, and an AI companion for stuck-on-a-problem help.

Start solving

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Progressive Hints + AI Companion

3-level reveal on every problem; AI chat that answers "explain differently", "give me a nudge", "what edge cases?" — never spoils the solution.

Try on Two Sum

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109 Traps + 105 Quiz Questions

Every trap callout in one appendix. 5-question quiz at the end of every pattern chapter — score is saved locally.

Skim traps

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How this compares

Side-by-side vs Grokking, NeetCode, TakeUForward, LeetCode Premium. Where this book wins and where it doesn't.

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Company Tracks — Meta / Google / Amazon

4-week curated problem sequence per company, calibrated to level. What each company actually asks and how to answer their way.

Meta interview kit

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🎯 Interview Day Kit

The 24-hour checklist. Night before + morning of + in-interview + emergency mode. Pin this the day before your loop.

See the checklist

Built by

Abhishek Singhal

Senior Software Engineer. Built this reference over months of solo work while preparing for senior/staff interviews. If you found this useful, connect with me on GitHub.

DSA Master Reference

Try it before you read it

▶

Run Java on any problem — no signup

CheerpJ WASM runtime, in-browser, on 205 problems.

💡

Progressive hints on every page

3 levels of help — general → specific → near-solution.

✨

AI companion per problem

Ask "explain differently", "give me a nudge", "what edge cases?"

🎯

Pattern quizzes with scoring

5 questions per pattern; 105 questions total. Tracks progress.

⭐

Practice streak

0 days

🎯

Track your progress

Create a browser-local profile — no email required. Progress syncs across all pages you visit.

🗓️ Personalized study plan

Tell me your timeline and I'll generate a plan.

Weeks until interviewTarget level

4 weeks = sprint. Recommended baseline: works for most senior interviews.

Week 1
- → Java foundations (ch06-10)
- → Sliding Window + Two Pointers + Hashing
- → One canonical per pattern
Week 2
- → Binary Search + BS on Answer
- → Fast/Slow + Prefix Sum + Monotonic Stack
- → Heap + Top-K + K-way Merge
Week 3
- → Trees + BSTs + Trie
- → Graphs + BFS + DFS + Topo + UF
- → Backtracking
Week 4
- → DP (Grid + Sequence + Interval + Bitmask)
- → Design + Greedy + Divide & Conquer
- → Weekly mocks, traps catalog, day-of kit

Open full Roadmap →

338

Pages (PDF)

Core patterns

205

Interactive problems

109

Interview traps

105

Quiz questions

✨

AI companion + Java runner on every page

Why this book exists

Most DSA references are one of two things: a textbook (dense theory, no interview signal) or a LeetCode grind list (500 problems, zero pattern recognition). This is neither.

Pattern-first — you learn to recognize what family a problem belongs to, then apply the right template.
Java-native — all code is idiomatic Java 17. No Python-style pseudocode.
Interview-calibrated — every problem has a "how would you defend this in an interview" script.
Learning notes on every line — why is Long.MIN_VALUE the seed and not 0? why long and not int? Every non-obvious decision is called out.

What's inside

Part I — Foundations: Java Data Structures primer, complexity model, Java gotchas, debugging DSA code
Part II — 21 Core Patterns: Sliding Window, Two Pointers, Prefix Sum, Binary Search, DP, Backtracking, Union-Find, and more
Part III — Data Structures in Depth: Arrays, Strings, Linked Lists, Trees, Heaps, Trie, Graphs, Segment Tree
Part IV — Cheat Sheets & Self-Check: templates, drills, problem index, mock transcripts, traps catalog

Also available as a searchable offline PDF

For flights, whiteboarding, or interview eve without WiFi. Same content as the website. Download from Releases.

What learners say

Interview outcomes from real users

"The pattern-recognition framework finally clicked after a week of using this. Passed my Meta E5 loop last month."

Software Engineer, Meta (L5)

🎯 Meta E5 offer

"Company tags saved me hours — I focused only on problems asked at my target companies. Interviewer literally asked one I had just done."

SDE, Amazon SDE II

🎯 Amazon SDE II offer

"The 'Progressive Hints' are a game-changer. I stopped just reading solutions and actually developed the muscle to reason through problems."

Backend Engineer, Google L4

🎯 Google L4 offer

"Every DSA book teaches you the same 20 problems. This one teaches you 21 patterns — a totally different level."

Staff Engineer, Fintech

🎯 Staff offer at fintech

Testimonials are anonymized composites drawn from user feedback. If you land your offer thanks to this reference, let me know — I collect a monthly "wall of wins".

☕

Free forever. Support keeps it that way.

If this reference helped land your offer, buy me a coffee. It funds the next batch of pattern videos.

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One curated problem + one hidden trap + one pattern insight, every Sunday. Unsubscribe anytime.

No spam. No affiliate junk. Weekly cadence. Curated by the author.

💡 Quick shortcuts

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DSA Master ReferenceZero to Hero for Senior/Staff Interviews

21 Core Patterns

Learning Notes on Every Line

8-Week Roadmap

205 Interactive Problems

Progressive Hints + AI Companion

109 Traps + 105 Quiz Questions

How this compares

Company Tracks — Meta / Google / Amazon

🎯 Interview Day Kit

Recently updated ​

Built by ​

Abhishek Singhal

DSA Master Reference ​

Try it before you read it ​

Why this book exists ​

What's inside ​

Also available as a searchable offline PDF ​

Recently updated