DSA for SDE‑1 (India): a 21‑day prep roadmap + daily checklist
by Anupam Bhatt
· February 14, 2026
Why this plan works (India SDE‑1 reality)
Most SDE‑1 screens in India reward pattern recognition, clean communication, and a small set of core DS topics done well.
Before you start (setup)
- Pick 1 language for interviews (Java/C++/Python/JS) and stick to it for 3 weeks.
- Maintain a single notes doc: patterns + mistakes + template snippets.
- Every day: 2 problems + 1 review. Don’t overdo quantity.
The 21‑day roadmap
Week 1 — Arrays/Strings + Hashing + Two pointers
- Day 1–2: arrays basics, prefix/suffix, frequency maps
- Day 3–4: strings, anagrams, sliding window basics
- Day 5–6: hashing patterns (two‑sum family, dedupe, counts)
- Day 7: review day (redo 6 problems without looking)
Week 2 — Stack/Queue + Binary search + Recursion
- Day 8–9: stack patterns (next greater, parentheses)
- Day 10–11: queues/deques, monotonic queue basics
- Day 12–13: binary search templates (first/last, answer space)
- Day 14: review + 1 timed mock
Week 3 — Linked list + Trees (core)
- Day 15–16: linked list (reverse, cycle, merge)
- Day 17–19: trees (DFS, BFS, height/diameter, LCA basics)
- Day 20: mixed mock (2 problems in 60–75 min)
- Day 21: final revision (your top 10 mistakes)
How to communicate (what gets you hired)
- Clarify constraints (n range, duplicates, sorted?)
- State approach + complexity
- Walk through 1 example
- Code with small checkpoints
- Test edge cases