Learn Data Structures and Algorithms

Written and maintained by the JBattle team · Last updated 5 September 2026

Data structures and algorithms is not a list of tricks to memorise; it is a small set of ideas that recombine. This track follows the order those ideas actually build in — how memory works, then what it costs, then the patterns that exploit both. Each lesson ends with practice, and each topic ends with a quiz so recall gets tested rather than assumed.

▶ Start with Memory layout

Topics: 3
Lessons: 10
Read time: 1 h 20 m
Practice problems: 39

Phase 1 · Foundations

01ArraysContiguous memory, O(1) access, and the four patterns built on it Memory layout · Traversal & operations · Two pointers · Sliding window · Prefix sum5 lessons02StringsImmutability, the cost of concatenation, and the classic interview patterns Immutability & cost · Palindromes & anagrams · Pattern matching3 lessons

Phase 2 · Lookup structures

01HashingO(1) lookup, collision handling, and the counting patterns built on maps How hash tables work · Frequency counting2 lessons

How to use this track

1. Follow the order. Each lesson assumes the one before it. Every page has previous and next buttons, so you can read the whole track without going back to a menu.

2. Do the practice. Lessons end with problems tagged by pattern, so you can tell whether you learned the idea or just the example.

3. Test recall, not recognition. A topic quiz at the end of each chapter is a far better check than re-reading the page.