Data Structures & Algorithms
37 pieces. Four tracks.Zero filler.
Hand-written explanations of the patterns, problems and designs that show up in real interviews — and real engineering. Each piece leads with the insight, then the code.
SSE 60-Day Interview Plan
A daily prep plan for Senior Software Engineer loops. Each day pairs one DSA pattern with an LLD problem, an HLD problem and a rotating tech focus — Java, Kafka, Cassandra, Spring Boot, Kubernetes and more.
Patterns
The 8 patterns behind 80% of interview problems. Spot them, and the solution stops being a memory test.
Open trackLeetCode-style problems
Hand-picked problems with the insight first, then the code. No 50-line solution before you've understood why.
Open trackLow-level design
Object-oriented design walkthroughs — Splitwise, Parking Lot, Vending Machine — with the tradeoffs spelled out.
Open trackHigh-level design
Distributed system designs — URL shortener, Twitter, Uber — with capacity numbers, components and where they break.
Open trackRecently added
Problems
Two Sum
Find two indices whose values sum to a target. The classic O(n) hashmap warm-up.
Problems
Longest Substring Without Repeating Characters
Sliding window with a 'last seen' index — O(n), single pass.
HLD
Design a URL Shortener
Bit.ly-class system: Base62 IDs, key-value store, edge cache, ~10× read/write skew.
HLD
Design Twitter (Timeline)
Fan-out on write vs. read, with a hybrid for celebrity accounts. The classic timeline trade-off.
LLD
Parking Lot
Multi-floor parking with size-based slot allocation, ticket lifecycle and pricing strategy.
LLD
Splitwise (Expense Sharing)
Track group expenses with arbitrary splits and minimise inter-user settlement transactions.