---
changelog:
  category: Topic
  version: 20260930.195303.000000000
date: '2026-09-30T19:53:03Z'
seo:
  description: >-
    Finished Wed, Sep 30, 2026, 3:53 PM ET: all 3 core problems closed, 3
    problems closed that day. Scheduled: Wed Sep 30, 2026 · Phase: Phase V —
    Decision Space…
title: Topic 24 — Intervals
type: changelog
---
<!-- release-topics: #26 -->
Finished Wed, Sep 30, 2026, 3:53 PM ET: all 3 core problems closed, 3 problems closed that day.

**Scheduled:** Wed Sep 30, 2026 · **Phase:** Phase V — Decision Space · **Topic:** #26 · **Builds on:** Topic 23

## Closed Sep 30 — the day the topic finished

| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
| --- | --- | --- | --- | --- | --- |
| #181 | LC 57 · Insert Interval | core | medium | Sep 30 | [py](https://github.com/prdlk/leetcode/blob/20260930.195303.000000000/work/1/Medium/Array/57.insert-interval.py) · [docs](https://lc.prd.lk/57) |
| #182 | LC 56 · Merge Intervals | core | medium | Sep 30 | [py](https://github.com/prdlk/leetcode/blob/20260930.195303.000000000/work/1/Medium/Array/56.merge-intervals.py) · [docs](https://lc.prd.lk/56) |
| #183 | LC 435 · Non-Overlapping Intervals | core | medium | Sep 30 | [py](https://github.com/prdlk/leetcode/blob/20260930.195303.000000000/work/1/Medium/Array/435.non-overlapping-intervals.py) · [docs](https://lc.prd.lk/435) |

## Open at release

| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
| --- | --- | --- | --- | --- | --- |
| #184 | LC 253 · Meeting Rooms II | optional | medium | — | — |
| #185 | LC 228 · Summary Ranges | optional | easy | — | — |
| #186 | LC 452 · Minimum Arrows to Burst Balloons | optional | medium | — | — |
| #187 | LC 920 · Number of Music Playlists | optional | hard | — | — |
| #223 | LC 986 · Interval List Intersections | optional | medium | — | — |

---

`20260930.195303.000000000` is [timever](https://gist.github.com/twolfson/de1b004dd22536b8e668) for the UTC instant the core set completed; it tags e1c8f1a, the last main commit before it.