---
changelog:
  category: Release
  version: 20260922.190245.000000000
date: '2026-09-22T19:02:45Z'
seo:
  description: >-
    Finished Tue, Sep 22, 2026, 3:02 PM ET: all 2 core problems closed, 2
    problems closed that day. Scheduled: Tue Sep 22, 2026 · Phase: Phase IV —
    Relational ·…
title: Topic 18 — Topological Sort
type: changelog
---
<!-- release-topics: #20 -->
Finished Tue, Sep 22, 2026, 3:02 PM ET: all 2 core problems closed, 2 problems closed that day.

**Scheduled:** Tue Sep 22, 2026 · **Phase:** Phase IV — Relational · **Topic:** #20 · **Builds on:** Topic 16

## Closed Sep 22 — the day the topic finished

| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
| --- | --- | --- | --- | --- | --- |
| #142 | LC 207 · Course Schedule | core | medium | Sep 22 | [py](https://github.com/prdlk/leetcode/blob/20260922.190245.000000000/work/1/Medium/Depth-First%20Search/207.course-schedule.py) · [docs](https://lc.prd.lk/207) |
| #143 | LC 210 · Course Schedule II | core | medium | Sep 22 | [py](https://github.com/prdlk/leetcode/blob/20260922.190245.000000000/work/1/Medium/Depth-First%20Search/210.course-schedule-ii.py) · [docs](https://lc.prd.lk/210) |

## Open at release

| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
| --- | --- | --- | --- | --- | --- |
| #144 | LC 1462 · Course Schedule IV | optional | medium | — | — |
| #145 | LC 269 · Alien Dictionary | deferred | hard | — | — |
| #216 | LC 802 · Find Eventual Safe States | optional | medium | — | — |

---

`20260922.190245.000000000` is [timever](https://gist.github.com/twolfson/de1b004dd22536b8e668) for the UTC instant the core set completed; it tags 0009075, the last main commit before it.