今日固定时间表
三块窗口固定：08:50-10:55 系统设计，14:30-16:15 算法，20:30-21:15 口述。
| 08:50-09:35 | 08:50-10:55 system design Ticketmaster 45m mock - 完整题：scope -> HLD -> Deep Dive 1 reservation/oversell -> Deep Dive 2 hot event/retry/reconciliation。 |
|---|---|
| 09:35-10:05 | 08:50-10:55 system design Online Auction 30m pressure - 从 bid order、durability、winner close rule 和 duplicate retry 追问。 |
| 10:05-10:35 | 08:50-10:55 system design Robinhood 30m pressure - 从 market update order、order consistency、cleanup 和 idempotency 追问。 |
| 10:35-10:55 | 08:50-10:55 system design DDIA 对照 - 用 uniqueness/total order/serializability 标出三题共同点和不可复用处。 |
| 14:30-16:15 | NeetCode Tag · Binary Search 三道题，每题 30m solve + 5m evidence，不能改 tag。 |
| 20:30-21:15 | 20:30-21:15 录音回听，选择最低分维度，写 repair sentence。 |
算法模块
连续 NeetCode Binary Search；每天 exactly 3 slots。
| # | Problem / mode | Pattern | Invariant | Bug risk | Time | Space |
|---|---|---|---|---|---|---|
| 1 | Search a 2D Matrix NEW · 30m solve + 5m evidence | flattened binary search | 2D coordinates map to one sorted virtual array. | Row/col conversion off-by-one. | O(log(mn)) | O(1) |
| 2 | Koko Eating Bananas NEW · 30m solve + 5m evidence | min feasible rate | If speed k works by h hours, any higher speed works. | Ceil division bug; lower bound starts at 0. | O(n log maxPile) | O(1) |
| 3 | Capacity to Ship Packages Within D Days NEW · 30m solve + 5m evidence | min feasible capacity | If capacity C ships within D days, any larger C works. | Lower bound below max package; incrementing day count at wrong time. | O(n log sum) | O(1) |
Hello Interview 精确目录
保留 live canonical heading title；day page 使用 direct section anchors。
今日不新增 Hello Interview section anchors；使用前五天的 evidence 做 mock 和 synthesis。
DDIA 精确决策卡
只使用 Ch8 和 Ch10 中直接解决今天设计决定的小节。
| 项目 | 项目问题 | 精确 DDIA subsection | 改变的系统决定 |
|---|---|---|---|
| Cross-domain | How do all three systems define the winning transaction? | Ch10 - 唯一性约束 | Unique winner is a system invariant: one seat owner, one accepted highest bid at close, one brokerage order state per client intent. |
三域 trace 任务
Winning transaction标出唯一线性化点：seat hold/sold、accepted bid at close、brokerage order/execution state。
Duplicate/retry failure给出 stable idempotency key、重复返回语义、旧 owner/stale version 被拒绝的证据。
Projection boundary说明哪些读可以陈旧：seat map、highest bid display、market price UI；哪些写不能陈旧。
本日 artifacts
项目脚本、音频、PDF 和 mock evidence 从当天直接打开。
今日产出、修复与英语 recall
| 课程角色 | CORE mock + FULL follow-ups |
|---|---|
| 必须交付 | Ticketmaster mock evidence + Auction/Robinhood pressure notes；每题一条 winning transaction 和一条 duplicate failure trace。 |
| 修复规则 | 如果 mock 少于两个 deep dives，重新跑 Ticketmaster，不进入 Day 7。 |
| English recall | English recall: The same retry pattern is safe only when the idempotency key maps to one durable intent. |
Detailed lecture notes, audio, recall scripts, PDFs, Staff Q&A, and mock packs are archived locally and are intentionally not published on this site.