DSAMotivator

Prefix Sum

Precompute running totals so any range query collapses to one subtraction.

The idea

The full written guide for Prefix Sumis 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#303 Range Sum Query - ImmutableEasy
  2. 2#724 Find Pivot IndexEasy
  3. 3#560 Subarray Sum Equals KMedium
  4. 4#974 Subarray Sums Divisible by KMedium
  5. 5#304 Range Sum Query 2D - ImmutableMedium
  6. 6#525 Contiguous ArrayMedium

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