Week 12 · Day 1 · 2026-10-12 MON · SYNTHESIS
30-project mechanism map
Exact Daily Blocks
Rebuild the full 30-project map from memory, then correct it against prior week artifacts as references only.
| 08:50-10:55 | System design Create the map with five fields for every project: project, core tension, reusable mechanism, invariant, high-value follow-up. Mark source-of-truth versus derived-state in every row. |
|---|---|
| 14:30-16:15 | NeetCode Backtracking Exactly three unique slots; each is 30m solve + 5m evidence. |
| 20:30-21:15 | Recall / mock repair Closed-book English recall: pick five random rows and explain why the invariant transfers. |
DDIA decision links
Only exact Ch13/Ch14 sections that change Week 12 decisions are linked.
| Decision question | Exact DDIA section | Design consequence |
|---|---|---|
| How do 30 prior projects become a reusable mechanism map instead of a name list? | Ch13 - 观察派生数据状态 | Every cached feed, dashboard, search result, ranking, or model answer is treated as derived state with observable lag, completeness, and rebuild path. |
| Which project outputs can be cached/materialized and which remain operational truth? | Ch13 - 物化视图和缓存 | The map separates source-of-truth state machines from materialized views so interview answers stop over-trusting caches. |
Algorithm block
Diagnostic decision: select Backtracking, not a weakest prior tag, because no production scorecard records a weaker tag and final week needs recursive state-space pruning under pressure.
| Slot | Problem | Pattern | Invariant | Bug risk | Time | Space |
|---|---|---|---|---|---|---|
| 1 | Subsets NEW · Backtracking · 30m solve + 5m evidence | binary include/exclude DFS | Each index is decided exactly once. | Forgetting to copy path before appending. | O(n 2^n) | O(n) stack + output |
| 2 | Subsets II NEW · Backtracking · 30m solve + 5m evidence | sorted DFS with duplicate skip | At one depth, equal values are chosen once as first element. | Skipping duplicates across depths instead of siblings. | O(n 2^n) | O(n) stack + output |
| 3 | Combination Sum NEW · Backtracking · 30m solve + 5m evidence | reuse-current DFS | The start index never decreases; target decreases to zero. | Advancing index after choosing a reusable candidate. | O(branch^depth) | O(target/min) stack |
Output
| Deliverable | Complete 30-project mechanism map and gap list; no new source exploration. |
|---|---|
| Artifacts | 30-project map Chinese synthesis Synthesis audio English recall Recall PDF Weak repair Repair audio Cohort crosswalk |
Detailed lecture notes, audio, recall scripts, PDFs, Staff Q&A, and mock packs are archived locally and are intentionally not published on this site.