Explore related knowledge and questions →

Question 13699: Reflexive Connectivity Includes a Length-Zero Path

On this page
  1. Original question and givens
  2. Definition and scope
  3. Step-by-step derivation
  4. Reverse checks
  5. Result
  6. This question review and source binding

Return to catalogue page 69

← Question derivation index · Original question batch

R0026-13699 · q-20261014-advance-20261028-r07-connected-component-0074

Original question and givens

Use the complete finite undirected loop-free simple graph on Fin(7)={0,…,6} with edge set=[[0, 4], [0, 6], [1, 2], [1, 5], [1, 6], [2, 5], [2, 6], [3, 4], [3, 6]]. Loops and duplicate undirected edges are forbidden. Connectivity is complete path reachability, not just one traversal fragment. Length-zero paths make every vertex reachable from itself, including isolated vertices. Do not switch to directed weak/strong, infinite or dynamic connectivity. left=2, right=0. Give (left,right,left_component,same_component?).

  • G001 — Use the complete finite undirected loop-free simple graph on Fin(7)={0,…,6} with edge set=[[0, 4], [0, 6], [1, 2], [1, 5], [1, 6], [2, 5], [2, 6], [3, 4], [3, 6]]. Loops and duplicate undirected edges are forbidden. Connectivity is complete path reachability, not just one traversal fragment. Length-zero paths make every vertex reachable from itself, including isolated vertices. Do not switch to directed weak/strong, infinite or dynamic connectivity. left=2, right=0. Give (left,right,left_component,same_component?).

Definition and scope

Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate.

Step-by-step derivation

S001 · implies

Before

full carrier Fin(7);raw undirected edges=[[0, 4], [0, 6], [1, 2], [1, 5], [1, 6], [2, 5], [2, 6], [3, 4], [3, 6]]

After

canonical simple edges=[[0, 4], [0, 6], [1, 2], [1, 5], [1, 6], [2, 5], [2, 6], [3, 4], [3, 6]];full adjacency rows=[[4, 6], [2, 5, 6], [1, 5, 6], [4, 6], [0, 3], [1, 2], [0, 1, 2, 3]]

Conditions: none

Build adjacency on the full carrier,rejecting loops and duplicate undirected edges.Vertices absent from edges retain empty rows;do not switch to directed connectivity.

Step identifiers and dependencies

Rule: component_full_undirected_graph_includes_isolates · Uses: G001

S002 · implies

Before

left vertex:start vertex=2;complete adjacency=[[4, 6], [2, 5, 6], [1, 5, 6], [4, 6], [0, 3], [1, 2], [0, 1, 2, 3]]

After

initial visited=[2];path to start=[2];edge length0

Conditions: none

The start reaches itself by a length-zero path.Even an isolated vertex must be included rather than omitted for having no edges.

Step identifiers and dependencies

Rule: component_zero_length_reflexive_path · Uses: G001, S001

S003 · implies

Before

left vertex:layer=0;frontier=[2];all frontier neighbors=[1, 5, 6]

After

previously seen=[2];new vertices=[1, 5, 6]

Conditions: none

At each layer inspect every neighbor of every frontier vertex,then add only unvisited distinct labels.Do not stop at a plausible-looking fragment.

Step identifiers and dependencies

Rule: component_complete_frontier_expansion · Uses: G001, S002

S004 · implies

Before

left vertex:new vertex=1;earliest frontier parent=2;parent path=[2]

After

append actual parent edge;reachable path=[2, 1]

Conditions: none

Extend the established parent path by an original graph edge,so every added vertex really is reachable.

Step identifiers and dependencies

Rule: component_each_new_vertex_path_witness · Uses: G001, S003

S005 · implies

Before

left vertex:new vertex=5;earliest frontier parent=2;parent path=[2]

After

append actual parent edge;reachable path=[2, 5]

Conditions: none

Extend the established parent path by an original graph edge,so every added vertex really is reachable.

Step identifiers and dependencies

Rule: component_each_new_vertex_path_witness · Uses: G001, S004

S006 · implies

Before

left vertex:new vertex=6;earliest frontier parent=2;parent path=[2]

After

append actual parent edge;reachable path=[2, 6]

Conditions: none

Extend the established parent path by an original graph edge,so every added vertex really is reachable.

Step identifiers and dependencies

Rule: component_each_new_vertex_path_witness · Uses: G001, S005

S007 · implies

Before

left vertex:layer=1;frontier=[1, 5, 6];all frontier neighbors=[0, 1, 2, 3, 5, 6]

After

previously seen=[1, 2, 5, 6];new vertices=[0, 3]

Conditions: none

At each layer inspect every neighbor of every frontier vertex,then add only unvisited distinct labels.Do not stop at a plausible-looking fragment.

Step identifiers and dependencies

Rule: component_complete_frontier_expansion · Uses: G001, S006

S008 · implies

Before

left vertex:new vertex=0;earliest frontier parent=6;parent path=[2, 6]

After

append actual parent edge;reachable path=[2, 6, 0]

Conditions: none

Extend the established parent path by an original graph edge,so every added vertex really is reachable.

Step identifiers and dependencies

Rule: component_each_new_vertex_path_witness · Uses: G001, S007

S009 · implies

Before

left vertex:new vertex=3;earliest frontier parent=6;parent path=[2, 6]

After

append actual parent edge;reachable path=[2, 6, 3]

Conditions: none

Extend the established parent path by an original graph edge,so every added vertex really is reachable.

Step identifiers and dependencies

Rule: component_each_new_vertex_path_witness · Uses: G001, S008

S010 · implies

Before

left vertex:layer=2;frontier=[0, 3];all frontier neighbors=[4, 6]

After

previously seen=[0, 1, 2, 3, 5, 6];new vertices=[4]

Conditions: none

At each layer inspect every neighbor of every frontier vertex,then add only unvisited distinct labels.Do not stop at a plausible-looking fragment.

Step identifiers and dependencies

Rule: component_complete_frontier_expansion · Uses: G001, S009

S011 · implies

Before

left vertex:new vertex=4;earliest frontier parent=0;parent path=[2, 6, 0]

After

append actual parent edge;reachable path=[2, 6, 0, 4]

Conditions: none

Extend the established parent path by an original graph edge,so every added vertex really is reachable.

Step identifiers and dependencies

Rule: component_each_new_vertex_path_witness · Uses: G001, S010

S012 · implies

Before

left vertex:layer=3;frontier=[4];all frontier neighbors=[0, 3]

After

previously seen=[0, 1, 2, 3, 4, 5, 6];new vertices=[]

Conditions: none

At each layer inspect every neighbor of every frontier vertex,then add only unvisited distinct labels.Do not stop at a plausible-looking fragment.

Step identifiers and dependencies

Rule: component_complete_frontier_expansion · Uses: G001, S011

S013 · implies

Before

left vertex:final visited=[0, 1, 2, 3, 4, 5, 6];all [vertex,neighbors,outside neighbors] rows=[[0, [4, 6], []], [1, [2, 5, 6], []], [2, [1, 5, 6], []], [3, [4, 6], []], [4, [0, 3], []], [5, [1, 2], []], [6, [0, 1, 2, 3], []]]

After

no edge leaves visited;every visited vertex has a path;visited equals full reachable set

Conditions: none

Path witnesses give visited⊆reachable.At completion no edge leaves visited.If a path reached outside,it would have a first leaving edge,a contradiction,so reachable⊆visited.Both directions establish the whole component,not a traversal order.

Step identifiers and dependencies

Rule: component_reachable_and_closed_set_completeness · Uses: G001, S012

S014 · implies

Before

left=2;right=0;whole left component=[0, 1, 2, 3, 4, 5, 6]

After

same component=Yes

Conditions: none

Compute the whole left component before testing the right label.Equal endpoints are connected by a zero-length path even if isolated.

Step identifiers and dependencies

Rule: component_membership_after_complete_reachability · Uses: G001, S013

Reverse checks

  • S014 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S013 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S012 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S011 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S010 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S009 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S008 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S007 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S006 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S005 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S004 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S003 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S002 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

(2, 0, [0, 1, 2, 3, 4, 5, 6], Yes)

The full substitutions and premise checks give the original answer; source identity,format and status are unchanged.

This question review and source binding

Review date: 2026-10-26

Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.

Source hashes and review receipts
  • input commit: 0f7be61e2c22317a4075561dc822c87d881a50db
  • original question SHA-256: 30c309955da9deef82d274663cd29d7dc66a26c5e7466a9a83e612d0f0764152
  • candidate record SHA-256: 68075bde75ca4788d3fa1ceec8e147a91aad8175963a8eedc96dda8e9b158459
  • semantic review receipt SHA-256: f335caca08574c9f949c141083c66655fee51c227d45d80a3ddb7d78f862d798
  • question-first witness SHA-256: cc7ba54738af91a6871fc1c20e45ad8f2b434392273fa334bd16a3b2238f4a77
  • Lean: NOT_RUN · human review: NOT_PERFORMED
Same-source full JSON