DSAMotivator

Arrays & Hashing

Trade memory for speed: hash maps turn O(n²) scans into O(n) lookups.

The idea

The full written guide for Arrays & Hashingis on its way. The practice progression below is live — it's the same curated, ordered list our users work through inside the app.

Practice progression

In this order, on LeetCode. Each one adds a wrinkle the previous one didn't have.

  1. 1#217 Contains DuplicateEasy
  2. 2#242 Valid AnagramEasy
  3. 3#1 Two SumEasy
  4. 4#49 Group AnagramsMedium
  5. 5#347 Top K Frequent ElementsMedium
  6. 6#238 Product of Array Except SelfMedium
  7. 7#36 Valid SudokuMedium
  8. 8#128 Longest Consecutive SequenceMedium
  9. 9#169 Majority ElementEasy

Knowing the pattern is half the job. Showing up daily is the other half.

DSAMotivator tracks this exact progression — with streaks, XP, and a map that fills in as you go.

Start free — 7 days