Merge pull request #67 from lufftw/review/pattern-union-find

review(union_find): Pattern quality review - Tier 2 assessment

Author: lufftw

docs/patterns/union_find/templates.md

@@ -777,8 +777,6 @@ equations = ["a==b", "c==d", "a!=d"]
 
 ---
 
----
-
 ## 7. Pattern Comparison
 
 ### 7.1 Union-Find vs DFS/BFS for Connectivity
@@ -862,8 +860,6 @@ def union_with_size(x, y):
 
 ---
 
----
-
 ## 8. Decision Framework
 
 ### 8.1 Quick Reference Decision Tree
@@ -955,8 +951,6 @@ idx = row * cols + col
 
 ---
 
----
-
 ## 9. Code Templates Summary
 
 ### 9.1 Template 1: Basic Union-Find Class

docs/reviews/pattern-review-log.md

@@ -64,7 +64,7 @@ This log records all pattern review findings, decisions, and resolutions. Each r
 | tree | Tier 2 | 2025-01-07 | 0/0/1/0 | Reviewed |
 | tree_dp | Pending | - | - | Queued |
 | trie | Pending | - | - | Queued |
-| union_find | Pending | - | - | Queued |
+| union_find | Tier 2 | 2025-01-07 | 0/0/1/0 | Reviewed |
 
 **Legend**: C=Critical, M=Major, m=Minor, n=Nit
 
@@ -553,4 +553,63 @@ END TEMPLATE
 
 ---
 
+## Union-Find Review - 2025-01-07
+
+### Files Reviewed
+- `docs/patterns/union_find/templates.md` (1107 lines)
+- `docs/patterns/union_find/intuition.md` (215 lines)
+
+### Reference Standards
+- Gold Standard: `sliding_window/templates.md`
+- Ontology Entry: `UnionFindConnectivity` from `ontology/api_kernels.toml`
+
+### Findings
+
+#### [UF-001]: Duplicate Section Separators
+
+| Field | Value |
+|-------|-------|
+| **Category** | Engineering |
+| **Severity** | Minor |
+| **Location** | `docs/patterns/union_find/templates.md:778-780, 863-865, 956-958` |
+| **Issue** | Double `---` separators appear between sections 6-7, 7-8, and 8-9, creating visual inconsistency. |
+| **Why It Matters** | Cosmetic issue affecting document consistency. Does not impact functionality. |
+| **Decision** | Fix |
+| **Resolution** | Removed duplicate separators (3 locations). |
+
+### Positive Observations (Not Issues)
+
+| Aspect | Assessment |
+|--------|------------|
+| **API Kernel Header** | ✅ `UnionFindConnectivity` with clear core mechanism description |
+| **Core Concepts** | ✅ Comprehensive Section 1: data structure, path compression, union by rank, O(α(n)) analysis |
+| **Pattern Variants** | ✅ 5 variants: Components, Cycle Detection, Equivalence Grouping, Network Connectivity, Constraint Satisfaction |
+| **Code Templates Summary** | ✅ Section 9 at end with 5 templates (Basic, Inline, Size-tracking, Cycle Detection, Constraints) |
+| **Decision Framework** | ✅ ASCII decision tree (Section 8) with feature selection guide |
+| **Visual Representations** | ✅ Excellent tree diagrams showing path compression and union by rank |
+| **Union-Find vs DFS** | ✅ Clear comparison table with use-case guidance |
+| **Index Mapping Patterns** | ✅ Section 8.4 covers 1-indexed, char indices, string mapping, grid coordinates |
+| **Intuition Quality** | ✅ 4 mental models: Forest View, Path Compression, Union by Rank, Cycle Detection |
+| **Common Pitfalls** | ✅ 3 pitfalls: no path compression, wrong index range, processing order |
+| **Practice Progression** | ✅ Level 1-4 problem sequence |
+
+### Summary
+
+| Category | Critical | Major | Minor | Nit | Total |
+|----------|----------|-------|-------|-----|-------|
+| Concept | 0 | 0 | 0 | 0 | 0 |
+| Explanation | 0 | 0 | 0 | 0 | 0 |
+| Engineering | 0 | 0 | 1 | 0 | 1 |
+| **Total** | 0 | 0 | 1 | 0 | **1** |
+
+### Tier Assessment
+- **Previous Tier**: Pending
+- **New Tier**: Tier 2 (Silver)
+- **Rationale**: Comprehensive Union-Find coverage with excellent visual diagrams explaining path compression and union by rank. The O(α(n)) complexity analysis is well-presented. Strong intuition.md with 4 mental models. The index mapping patterns section (8.4) is particularly useful for handling different input formats. Minor cosmetic issue with duplicate separators.
+
+### Action Items
+- [x] Fix duplicate section separators (3 locations)
+
+---
+
 *Pattern Review Log - NeetCode Practice Framework*