---
changelog:
  category: Release
  version: 20260824.182003.000000000
date: '2026-08-24T18:20:03Z'
seo:
  description: >-
    Finished Mon, Aug 24, 2026, 2:20 PM ET: all 3 core problems closed, 3
    problems closed that day. Scheduled: Tue Aug 18, 2026 · Phase: Phase I —
    Linear…
title: Topic 02 — Prefix Sum
type: changelog
---
<!-- release-topics: #4 -->
Finished Mon, Aug 24, 2026, 2:20 PM ET: all 3 core problems closed, 3 problems closed that day.

**Scheduled:** Tue Aug 18, 2026 · **Phase:** Phase I — Linear Structures · **Topic:** #4 · **Builds on:** Topic 1

## Closed Aug 24 — the day the topic finished

| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
| --- | --- | --- | --- | --- | --- |
| #36 | LC 303 · Range Sum Query | core | easy | Aug 24 | [js](https://github.com/prdlk/leetcode/blob/20260824.182003.000000000/work/Easy/Array/303.range-sum-query-immutable.js) · [docs](https://lc.prd.lk/303) |
| #37 | LC 238 · Product of Array Except Self | core | medium | Aug 24 | [js](https://github.com/prdlk/leetcode/blob/20260824.182003.000000000/work/Medium/Array/238.product-of-array-except-self.js) · [docs](https://lc.prd.lk/238) |
| #38 | LC 560 · Subarray Sum Equals K | core | medium | Aug 24 | [js](https://github.com/prdlk/leetcode/blob/20260824.182003.000000000/work/Medium/Array/560.subarray-sum-equals-k.js) · [docs](https://lc.prd.lk/560) |

## Open at release

| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
| --- | --- | --- | --- | --- | --- |
| #39 | LC 525 · Contiguous Array | optional | medium | — | — |
| #40 | LC 974 · Subarray Sums Divisible by K | optional | medium | — | — |

---

`20260824.182003.000000000` is [timever](https://gist.github.com/twolfson/de1b004dd22536b8e668) for the UTC instant the core set completed; it tags 32a41bd, the last main commit before it.