WEEK 09 · 2026.09.21-09.27 · WRITER GATE
Day 5 - Yelp TRANSFER: blind attempt and geo candidate retrieval
2026-09-25 · FRI · 把搜索迁移到本地商户发现：geo cell candidates、text/category filters、rating aggregate and stable map result order。
今日固定时间表
三个学习窗口必须保持 exactly 08:50-10:55, 14:30-16:15, 20:30-21:15。
| 08:50-09:25 | 08:50-10:55 system design Blind transfer attempt: start with retrieval/rank split, then force geo and review constraints. |
|---|---|
| 09:25-10:05 | 08:50-10:55 system design Read Yelp headings through HLD and three functional paths. |
| 10:05-10:35 | 08:50-10:55 system design Geo search: S2/geohash/grid candidates, boundary second-pass filter and distance/rating/relevance ranking. |
| 10:35-10:55 | 08:50-10:55 system design DDIA Ch4 multidimensional and composite index decisions. |
| 14:30-16:15 | NeetCode Graphs Three contiguous Graphs slots below; no other tag. |
| 20:30-21:15 | Yelp transfer script audio pass: explain why rating is derived and moderation-aware. |
算法模块
NeetCode Graphs, exactly three slots today, contiguous slots 13-15 of 21.
| # | Problem / mode | Pattern | Invariant | Bug risk | Time | Space |
|---|---|---|---|---|---|---|
| 13 | Pacific Atlantic Water Flow Graphs · NEW · 30m solve + 5m evidence | reverse ocean reachability | cells are answers only if reachable from both oceans in reverse climb | flowing downhill from every cell | O(mn) | O(mn) |
| 14 | Surrounded Regions Graphs · NEW · 30m solve + 5m evidence | boundary-safe flood fill | only regions not connected to boundary O are flipped | flipping before preserving boundary-connected cells | O(mn) | O(mn) |
| 15 | Rotting Oranges Review Graphs · NEW · 30m solve + 5m evidence | multi-source BFS review | fresh count reaches zero iff all oranges rot | forgetting unreachable fresh oranges | O(mn) | O(mn) |
今日产出
| 必须交付 | Yelp transfer blind attempt plus link map first half. |
|---|---|
| 修复规则 | If answer starts with text search only, redraw it as geo candidates first, then text/filter/rank. |
Hello Interview 精确目录
使用 live heading 的 original title 和 direct anchor。
| 项目 | Level | 精确 canonical section | Disposition | Day |
|---|---|---|---|---|
| Yelp | h2 | Understanding the Problem | blind attempt then reading | Day 5 |
| Yelp | h3 | Functional Requirements | blind attempt then reading | Day 5 |
| Yelp | h3 | Non-Functional Requirements | blind attempt then reading | Day 5 |
| Yelp | h3 | Constraints | blind attempt then reading | Day 5 |
| Yelp | h2 | The Set Up | blind attempt then reading | Day 5 |
| Yelp | h3 | Defining the Core Entities | blind attempt then reading | Day 5 |
| Yelp | h3 | The API | blind attempt then reading | Day 5 |
| Yelp | h2 | High-Level Design | blind attempt then reading | Day 5 |
| Yelp | h3 | 1) Users should be able to search for businesses | blind attempt then reading | Day 5 |
| Yelp | h3 | 2) Users should be able to view businesses | blind attempt then reading | Day 5 |
| Yelp | h3 | 3) Users should be able to leave reviews on businesses | blind attempt then reading | Day 5 |
DDIA 精确决策卡
Only DDIA Ch4 and Ch13 decision links are allowed.
| Day | Project | Decision | Link |
|---|---|---|---|
| Day 5 | Yelp | geo search uses multidimensional indexes or grid cells, not naked lat/lng scans | https://ddia.vonng.com/ch4/#sec_storage_multidimensional |
| Day 5 | Yelp | category + price + open_now + distance are composite filter/rank constraints | https://ddia.vonng.com/ch4/#sec_storage_index_multicolumn |
Artifacts
PDF is intentionally absent; Week 9 requires MP3 only for the FULL/TRANSFER scripts.
Detailed lecture notes, audio, recall scripts, PDFs, Staff Q&A, and mock packs are archived locally and are intentionally not published on this site.