Build it
8 builds, 32 steps. Each one is a real thing assembled across several files, one rule at a time — not a function with a hole in it. Every step runs against tests in your browser.
Data structures & algorithms
The structures themselves, built from nothing rather than imported.
- Singly Linked ListConstruct a Singly Linked List with ListNode pointers, append, prepend, index-based insertion, deletion, and in-place reversal.4 stepsjavascript · pythoneasy
- Binary Search TreeConstruct a Binary Search Tree with node pointers, recursive insertion, lookup, in-order traversal, and 3-case deletion.4 stepsjavascript · pythonmedium
- Hash MapConstruct a high-performance hash map with bucket arrays, modular hashing, collision chaining, and dynamic rehashing.4 stepsjavascript · pythonmedium
- LRU CacheBuild a fixed-size cache that throws away whatever was used least recently.4 stepsjavascript · pythonmedium
- Binary Min-HeapConstruct an array-backed binary min-heap with parent/child arithmetic, siftUp, siftDown, and linear-time heapify.4 stepsjavascript · pythonmedium
- Prefix Tree (Trie)Construct an n-ary Prefix Tree with character node branching, word insertion, prefix search, and auto-complete.4 stepsjavascript · pythonmedium
Real-world systems
The pieces of infrastructure you have used without opening.
Design patterns
Named solutions, built small enough to see the shape.
Builds assume the pattern rather than teach it. If one is unfamiliar, the DSA path and the problem sets cover the same ground first — a recommendation, never a lock. Nothing here is closed to anyone.