High Level Design
End-to-end design of a URL shortening service — estimations, API design, 301 vs 302 redirects, hash functions with collision resolution, base62 encoding, and the deep-dive read/write paths.
DSA
Covers: Brute Force, Better, Optimal. Optimal — Time O(n), Space O(n).
Covers: sorting Based, Better, Union Find. Optimal — Time O(n), Space O(n).
Hashing & Sorting problem — solution with code and analysis.
Two Pointer approach. Optimal — Time O(n), Space O(1).
Covers: Sorting + Hashing, character counts Based key. Optimal — Time O(n * k), Space O(n * k).