Graphs -> Tree Isomorphism

Canonical subtree encoding for rooted unordered trees, with unrooted comparison handled by trying one or two tree centers first.

• Topic slug: graphs/tree-isomorphism
• Tutorial page: Open tutorial
• Ladder page: Open ladder
• Repo problems currently tagged here: 1
• Repo companion pages: 5
• Curated external problems: 2

Microtopics

• rooted-tree-isomorphism
• canonical-encoding
• ahu-style
• tree-centers
• unordered-children
• subtree-signatures

Learning Sources

Source	Type
Competitive Programming 4 contents	Reference
CSES Tree Isomorphism I	Practice
CSES Tree Isomorphism II	Practice

Repo Companion Material

Material	Type
Tree Isomorphism hot sheet	quick reference
Tree Isomorphism I note	flagship note
Trees tutorial	compare point
Template Library exact starter route	starter route
Graph cheatsheet	quick reference

Curated External Problems

Core

Problem	Source	Difficulty	Context	Style	Prerequisites	Tags	Why it fits
Tree Isomorphism I	CSES	Hard	Canonical Encoding	Bottom-Up Canonicalization; Postorder; Structural Comparison	Rooted Tree; DFS; Parent-Child Structure	Rooted Tree; Canonical Form; Unordered Children	The clean rooted benchmark where the whole task is comparing two unordered rooted trees by canonical subtree types.

Stretch

Problem	Source	Difficulty	Context	Style	Prerequisites	Tags	Why it fits
Tree Isomorphism II	CSES	Hard	Tree Centers	Center Rooting; Bottom-Up Canonicalization; Structural Comparison	Tree Isomorphism I; Rooted Tree	Unrooted Tree; Centers; Canonical Form	The natural unrooted sibling: normalize by one or two centers, then reuse the rooted canonical-encoding primitive.

Repo Problems

Code	Title	Fit	Difficulty	Pattern	Note	Solution
TREEISOMORPHISM1	Tree Isomorphism I	primary	hard	-	Note	Code

Regeneration

python3 scripts/generate_problem_catalog.py