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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 ​

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.