---
changelog:
  category: Release
  version: 20260922.165949.000000000
date: '2026-09-22T16:59:49Z'
seo:
  description: >-
    Finished Tue, Sep 22, 2026, 12:59 PM ET: all 2 core problems closed, 2
    problems closed that day. Scheduled: Tue Sep 22, 2026 · Phase: Phase IV —
    Relational ·…
title: Topic 17 — Graph BFS
type: changelog
---
<!-- release-topics: #19 -->
Finished Tue, Sep 22, 2026, 12:59 PM ET: all 2 core problems closed, 2 problems closed that day.

**Scheduled:** Tue Sep 22, 2026 · **Phase:** Phase IV — Relational · **Topic:** #19 · **Builds on:** Topic 12 + visited set — shortest path unweighted

## Closed Sep 22 — the day the topic finished

| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
| --- | --- | --- | --- | --- | --- |
| #137 | LC 994 · Rotting Oranges | core | medium | Sep 22 | [py](https://github.com/prdlk/leetcode/blob/20260922.165949.000000000/work/1/Medium/Array/994.rotting-oranges.py) · [docs](https://lc.prd.lk/994) |
| #138 | LC 127 · Word Ladder | core | hard | Sep 22 | [py](https://github.com/prdlk/leetcode/blob/20260922.165949.000000000/work/1/Hard/Hash%20Table/127.word-ladder.py) · [docs](https://lc.prd.lk/127) |

## Open at release

| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
| --- | --- | --- | --- | --- | --- |
| #139 | LC 286 · Walls and Gates | optional | medium | — | — |
| #140 | LC 433 · Minimum Genetic Mutation | optional | medium | — | — |
| #141 | LC 909 · Snakes and Ladders | optional | medium | — | — |
| #215 | LC 1091 · Shortest Path in Binary Matrix | optional | medium | — | — |

---

`20260922.165949.000000000` is [timever](https://gist.github.com/twolfson/de1b004dd22536b8e668) for the UTC instant the core set completed; it tags 26085cc, the last main commit before it.