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feat: add NeetCode roadmap extractor with dependency graph

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- extract.mjs: idempotent script that fetches neetcode.io JS chunks,
  extracts topic dependency graph (18 topics, 21 edges) and problems
  (965 total, 199 NeetCode 150)
- out/roadmap.json: full data (graph + all problems + courses)
- out/roadmap-neetcode150.json: filtered to NeetCode 150 only
- out/roadmap.dot: Graphviz visualization
- out/roadmap.org: org-mode with TODO checklists, Python/C++ links
- neetcode-roadmap-graph.json: standalone edge list
- neetcode-roadmap.dot: standalone DOT file

Also reformats subarray table in qn_00.org
This commit is contained in:
Wong Ding Feng
2026-06-01 02:07:20 +08:00
parent f603236a48
commit b4f25ab87b
9 changed files with 12755 additions and 21 deletions
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org/questions/qn_00.org
+21 -21
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@@ -695,18 +695,18 @@ Time: O(n * 32), Space: O(32) per step
What is the master keyword-to-algorithm mapping for subarray problems?
** Back
| Problem Phrase | Array Property | Algorithm |
|---------------|---------------|-----------|
| "Continuous subarray + Sum = K" | Only positive numbers | **Sliding Window** (O(1) space) |
| "Continuous subarray + Sum = K" | Positive & negative | **Prefix Sum + Hash Map** (O(n) space) |
| "Divisible by K" or "Multiple of X" | Any numbers | **Prefix Remainder + Hash Map** (sum % K) |
| "Equal number of X and Y" | Any numbers | **Value Mapping** (X→1, Y→-1) + Prefix Sum Map |
| "Maximum / Minimum Sum" | Any numbers | **Kadane's Algorithm** (DP) |
| "Subarray Sum + Frequent Updates" | Element mutations | **Fenwick Tree / Segment Tree** |
| "Subarray product = K" | No zeros | **Prefix Product** (division) |
| "Subarray product positive/negative" | Any numbers | **Parity tracking** of negative count |
| "Subarray XOR = K" | Any numbers | **Prefix XOR + Hash Map** |
| "Subarray OR / AND" | Any numbers | **Set of results** (bounded by 32 changes) |
| Problem Phrase | Array Property | Algorithm |
|--------------------------------------+-----------------------+----------------------------------------------|
| "Continuous subarray + Sum = K" | Only positive numbers | **Sliding Window** (O(1) space) |
| "Continuous subarray + Sum = K" | Positive & negative | **Prefix Sum + Hash Map** (O(n) space) |
| "Divisible by K" or "Multiple of X" | Any numbers | **Prefix Remainder + Hash Map** (sum % K) |
| "Equal number of X and Y" | Any numbers | **Value Mapping** (X→1, Y→-1) + Prefix Sum Map |
| "Maximum / Minimum Sum" | Any numbers | **Kadane's Algorithm** (DP) |
| "Subarray Sum + Frequent Updates" | Element mutations | **Fenwick Tree / Segment Tree** |
| "Subarray product = K" | No zeros | **Prefix Product** (division) |
| "Subarray product positive/negative" | Any numbers | **Parity tracking** of negative count |
| "Subarray XOR = K" | Any numbers | **Prefix XOR + Hash Map** |
| "Subarray OR / AND" | Any numbers | **Set of results** (bounded by 32 changes) |
* Subarray Sum — Modular Arithmetic Insight [algorithm:interview]
:PROPERTIES:
@@ -747,15 +747,15 @@ The core philosophy of prefix sums is: **accumulate history as you traverse line
This generalizes far beyond addition:
| Problem | Mapping | Reduces To |
|---------|---------|-----------|
| Equal 0s and 1s | 0→-1, 1→+1 | Subarray sum = 0 |
| Equal odd/even | even→+1, odd→-1 | Subarray sum = 0 |
| Equal vowels/consonants | vowel→+1, consonant→-1 | Subarray sum = 0 |
| Equal A/B/C counts | Track (c_A-c_B, c_B-c_C) | Prefix state tuple repeats |
| Subarray product | Prefix product | Division (handle zeros) |
| Subarray XOR | Prefix XOR | XOR is invertible |
| Subarray sum | Prefix sum | Subtraction |
| Problem | Mapping | Reduces To |
|-------------------------+--------------------------+----------------------------|
| Equal 0s and 1s | 0→-1, 1→+1 | Subarray sum = 0 |
| Equal odd/even | even→+1, odd→-1 | Subarray sum = 0 |
| Equal vowels/consonants | vowel→+1, consonant→-1 | Subarray sum = 0 |
| Equal A/B/C counts | Track (c_A-c_B, c_B-c_C) | Prefix state tuple repeats |
| Subarray product | Prefix product | Division (handle zeros) |
| Subarray XOR | Prefix XOR | XOR is invertible |
| Subarray sum | Prefix sum | Subtraction |
The pattern:
1. Define a state that accumulates as you traverse