The Code NotebookCrack your tech interview, one page at a time
Simple, notebook-style lessons on data structures, algorithms and Java, made by a developer with 7 years of experience at a product company. Watch free, read the notes, practise the right problems.
Java backend developer · teaching what actually gets asked
Latest lessons
Hashing (HashMap & HashSet)
How HashMap works inside, equals & hashCode, Map shortcuts, and 5 patterns: counting, Two Sum, seen set, prefix sum + map, top K.
Strings
Immutable strings, == vs equals, StringBuilder, char math, palindromes, anagrams, expand around center and 4 Java string traps.
Arrays
How arrays work, 4 Java array traps, and 6 patterns: Kadane, running minimum, reverse trick, Dutch flag, prefix & suffix, in-place marking.
Bit Manipulation
Binary, the 7 bit operators, x & (x-1), XOR magic, bitmask subsets, counting bits and 4 Java traps.
📓 Notes for every video
Key ideas, Java code, cost tables and a practice list on every lesson page.
✅ Track your progress
Create a free account and tick off lessons from your dashboard.
🎯 Interview-first
Edge cases, follow-up questions and traps interviewers actually use.
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