12-Week Roadmap — SDE3+ Prep
A phased plan that moves from patterns → problems → system design → mock loops. Each week ends with a self-test.
Week 0 — Setup (1–2 days)
- Read the DSA mind-map home, Problem mind-map template.
- Skim the Patterns overview and Pattern recognition cheatsheet.
- Pick your daily cadence: 3 problems/day (90 days → 270 problems) or 2 problems/day (more depth).
Phase 1 — Pattern Foundations (Weeks 1–2)
Build the recognition reflex first. Don't grind problems yet — internalize why each pattern exists.
| Day | Pattern | Problems to skim (not solve) |
|---|---|---|
| 1 | Two Pointers | 167, 11, 15 |
| 2 | Sliding Window | 3, 76, 424 |
| 3 | Fast & Slow Pointers | 141, 142, 287 |
| 4 | Binary Search (+ on answer) | 704, 33, 875 |
| 5 | Stack / Monotonic Stack | 20, 739, 84 |
| 6 | Heap / Top-K | 215, 347, 23 |
| 7 | Review + cheat sheet drill | — |
| 8 | BFS | 102, 994, 127 |
| 9 | DFS / Backtracking | 200, 79, 39 |
| 10 | Trees (BFS/DFS/DP-on-trees) | 104, 124, 297 |
| 11 | Graphs (BFS/DFS/Topo) | 207, 210, 269 |
| 12 | Union-Find | 547, 684, 721 |
| 13 | DP intro (1D) | 70, 198, 322 |
| 14 | Review + recognition quiz | — |
Outcome: when shown a problem, you can name the pattern in <30 seconds.
Phase 2 — Easy + Medium grind (Weeks 3–6)
Solve all curated Easy + Medium (~180 problems) using each problem's mind-map page. Order by topic, not difficulty.
Cycle:
- Mon–Fri: 3 problems/day × topic
- Sat: review week's pitfalls + edge cases
- Sun: timed mock (2 mediums in 90 min)
| Week | Topics |
|---|---|
| 3 | arrays-hashing, two-pointers, sliding-window |
| 4 | stack, binary-search, linked-list |
| 5 | trees, tries, heap-priority-queue, backtracking |
| 6 | graphs, intervals, greedy, dp-1d |
Phase 3 — Hards + DP/Graphs depth (Weeks 7–8)
~70 Hards including SDE3-tier (DP-2D, advanced graphs, design coding like LFU/AllOne).
- 2 Hards/day, with full walkthrough write-up.
- Re-do any Hard you couldn't solve cold within 7 days.
Phase 4 — System Design Fundamentals (Week 9)
| Day | Topic |
|---|---|
| 1 | Scalability, latency vs throughput, back-of-envelope |
| 2 | CAP / PACELC, consistency models |
| 3 | Availability math, idempotency |
| 4 | Networking essentials, security basics |
| 5 | Building blocks: LB, CDN, cache |
| 6 | Building blocks: MQ, pub/sub, API gateway, rate limiter |
| 7 | Building blocks: SQL vs NoSQL, sharding, replication, consensus |
Phase 5 — HLD case studies (Week 10)
3 HLDs/day from high-level design case studies. For each, write your own 1-page TL;DR before reading the full doc — then diff.
Day-by-day suggested order: URL shortener → Pastebin → Twitter → Instagram → WhatsApp → News feed → Typeahead → Notification → Rate limiter → Distributed cache → Uber → Google Maps → Dropbox → YouTube → Netflix → Search engine → Web crawler → Ad-click aggregator → Payment system → Google Drive.
Phase 6 — LLD / OOD + Design Patterns (Week 11)
| Day | LLD |
|---|---|
| 1 | Parking Lot, Elevator |
| 2 | Splitwise, BookMyShow |
| 3 | LRU Cache, LFU Cache |
| 4 | Chess, Tic-Tac-Toe, Snake & Ladder |
| 5 | Cab Booking, Restaurant Ordering |
| 6 | Logger, Rate Limiter (LLD), ATM, Vending Machine |
| 7 | Design Patterns review (GoF + concurrency) |
Phase 7 — Mocks + Behavioral (Week 12)
- 5 full mock loops (2 DSA + 1 HLD + 1 LLD + 1 behavioral).
- Read the Behavioral STAR guide. Draft 8 stories using STAR.
- Review Company interview playbooks for the company you target.
Daily ritual (every phase)
- 5 min: skim yesterday's pitfalls.
- 45 min: solve cold (no peeking).
- 15 min: write the mind-map (or fill the template) for today's problem.
- 5 min: tag pattern + add to your "redo deck" if you struggled.
Done definition
You're ready when you can:
- Name a pattern from a problem statement in <30 sec.
- Code optimal in <25 min for any Medium, <40 min for any Hard.
- Drive an HLD for any new system using the RESHADED framework end-to-end in 45 min.
- Walk through any LLD with class diagram + tradeoffs in 30 min.
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