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Question 23219: One Full-Input Final Path Suffices Despite Dead Branches

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

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R0045-23219 · q-20261014-advance-20261111-r07-nondeterministic-finite-automaton-0069

Original question and givens

Use the complete finite epsilon-NFA: states=[s18, m18, f18, d18], alphabet=[a18, b18], start=s18, final_states=[f18], transitions=[[s18, null, m18], [s18, null, d18], [m18, a18, m18], [m18, b18, f18]]. Transitions are [from,input symbol or null,to]; null is epsilon and consumes no input. States are nonempty because the start belongs to them, but alphabet/final sets and the transition relation may be empty. The relation may be multivalued, not deterministic or total. A configuration is [state,input position]; acceptance requires one finite path consuming the entire input and ending final. Input=[a18, a18, b18], supplied path=[[s18, 0], [m18, 0], [m18, 1], [m18, 2], [f18, 3]]. Give (input, path, transition_indices, valid_path, accepted, certificate).

  • G001 — Use the complete finite epsilon-NFA: states=[s18, m18, f18, d18], alphabet=[a18, b18], start=s18, final_states=[f18], transitions=[[s18, null, m18], [s18, null, d18], [m18, a18, m18], [m18, b18, f18]]. Transitions are [from,input symbol or null,to]; null is epsilon and consumes no input. States are nonempty because the start belongs to them, but alphabet/final sets and the transition relation may be empty. The relation may be multivalued, not deterministic or total. A configuration is [state,input position]; acceptance requires one finite path consuming the entire input and ending final. Input=[a18, a18, b18], supplied path=[[s18, 0], [m18, 0], [m18, 1], [m18, 2], [f18, 3]]. Give (input, path, transition_indices, valid_path, accepted, certificate).

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

source operation=nfa-accepting-path-witness;original snapshot and mathematics retained

After

explicit ordered source output fields=[input, path, transition_indices, valid_path, accepted, certificate]

Conditions: none

Retain the historical interface marker while listing source fields without JavaScript.Tags and No retain their claim scope;source-protocol ordering is not a mathematical proof.

Step identifiers and dependencies

Rule: source_ordered_interface_explicit_without_javascript · Uses: G001

S002 · implies

Before

ORIGINAL transition index=0;[from,input_or_null,to]=[s18, null, m18];state carrier=[s18, m18, f18, d18];alphabet=[a18, b18]

After

state endpoints legal;symbol either declared input or null EPS consuming0;ORIGINAL row position retained,including duplicate rows

Conditions: none

This is a relation,not a total single-valued function.Retain duplicate,multivalued and missing edges;null consumes0 and is not an alphabet string.

Step identifiers and dependencies

Rule: nfa_EVERY_original_relation_row_roles_empty_multi_EPS_legal · Uses: G001, S001

S003 · implies

Before

ORIGINAL transition index=1;[from,input_or_null,to]=[s18, null, d18];state carrier=[s18, m18, f18, d18];alphabet=[a18, b18]

After

state endpoints legal;symbol either declared input or null EPS consuming0;ORIGINAL row position retained,including duplicate rows

Conditions: none

This is a relation,not a total single-valued function.Retain duplicate,multivalued and missing edges;null consumes0 and is not an alphabet string.

Step identifiers and dependencies

Rule: nfa_EVERY_original_relation_row_roles_empty_multi_EPS_legal · Uses: G001, S002

S004 · implies

Before

ORIGINAL transition index=2;[from,input_or_null,to]=[m18, a18, m18];state carrier=[s18, m18, f18, d18];alphabet=[a18, b18]

After

state endpoints legal;symbol either declared input or null EPS consuming0;ORIGINAL row position retained,including duplicate rows

Conditions: none

This is a relation,not a total single-valued function.Retain duplicate,multivalued and missing edges;null consumes0 and is not an alphabet string.

Step identifiers and dependencies

Rule: nfa_EVERY_original_relation_row_roles_empty_multi_EPS_legal · Uses: G001, S003

S005 · implies

Before

ORIGINAL transition index=3;[from,input_or_null,to]=[m18, b18, f18];state carrier=[s18, m18, f18, d18];alphabet=[a18, b18]

After

state endpoints legal;symbol either declared input or null EPS consuming0;ORIGINAL row position retained,including duplicate rows

Conditions: none

This is a relation,not a total single-valued function.Retain duplicate,multivalued and missing edges;null consumes0 and is not an alphabet string.

Step identifiers and dependencies

Rule: nfa_EVERY_original_relation_row_roles_empty_multi_EPS_legal · Uses: G001, S004

S006 · implies

Before

ORIGINAL states=[s18, m18, f18, d18],alphabet=[a18, b18],start=s18,final_states=[f18];complete relation=[[s18, null, m18], [s18, null, d18], [m18, a18, m18], [m18, b18, f18]]

After

states nonempty with actual start;alphabet/final set/relation MAY be EMPTY;definition qualification does NOT prove determinism,totality,DFA equivalence or a successful run

Conditions: none

An empty final set is legal and recognizes the empty language;an empty alphabet is legal too.A qualified definition supplies no accepting path,determinism or DFA-equivalence proof.

Step identifiers and dependencies

Rule: nfa_qualified_definition_EMPTY_alphabet_finals_edges_allowed · Uses: G001, S005

S007 · implies

Before

ORIGINAL input=[a18, a18, b18];ALL legal raw path configs=[[s18, 0], [m18, 0], [m18, 1], [m18, 2], [f18, 3]]

After

first configuration EXACT actual start=[s18, 0];this is not yet validity or acceptance

Conditions: none

First qualify every state/position and the exact initial configuration.A list of legal configurations need not have legal transitions.

Step identifiers and dependencies

Rule: nfa_actual_path_initial_and_structural_configurations_required · Uses: G001, S006

S008 · implies

Before

ORIGINAL path step=0;from=[s18, 0];to=[m18, 0];input=[a18, a18, b18]

After

ALL [ORIGINAL transition index,next_or_null] rows=[[0, [m18, 0]], [1, [d18, 0]], [2, null], [3, null]];FIRST matching index=0

Conditions: none

Take the first actual match in original transition order,including duplicate edges.Null advances0;a symbol advances1 and must match the original input.On failure retain prior partial indices;a later final state cannot repair the step.

Step identifiers and dependencies

Rule: nfa_EVERY_path_step_FIRST_ORIGINAL_transition_and_input_update · Uses: G001, S007

S009 · implies

Before

ORIGINAL path step=1;from=[m18, 0];to=[m18, 1];input=[a18, a18, b18]

After

ALL [ORIGINAL transition index,next_or_null] rows=[[0, null], [1, null], [2, [m18, 1]], [3, null]];FIRST matching index=2

Conditions: none

Take the first actual match in original transition order,including duplicate edges.Null advances0;a symbol advances1 and must match the original input.On failure retain prior partial indices;a later final state cannot repair the step.

Step identifiers and dependencies

Rule: nfa_EVERY_path_step_FIRST_ORIGINAL_transition_and_input_update · Uses: G001, S008

S010 · implies

Before

ORIGINAL path step=2;from=[m18, 1];to=[m18, 2];input=[a18, a18, b18]

After

ALL [ORIGINAL transition index,next_or_null] rows=[[0, null], [1, null], [2, [m18, 2]], [3, null]];FIRST matching index=2

Conditions: none

Take the first actual match in original transition order,including duplicate edges.Null advances0;a symbol advances1 and must match the original input.On failure retain prior partial indices;a later final state cannot repair the step.

Step identifiers and dependencies

Rule: nfa_EVERY_path_step_FIRST_ORIGINAL_transition_and_input_update · Uses: G001, S009

S011 · implies

Before

ORIGINAL path step=3;from=[m18, 2];to=[f18, 3];input=[a18, a18, b18]

After

ALL [ORIGINAL transition index,next_or_null] rows=[[0, null], [1, null], [2, null], [3, [f18, 3]]];FIRST matching index=3

Conditions: none

Take the first actual match in original transition order,including duplicate edges.Null advances0;a symbol advances1 and must match the original input.On failure retain prior partial indices;a later final state cannot repair the step.

Step identifiers and dependencies

Rule: nfa_EVERY_path_step_FIRST_ORIGINAL_transition_and_input_update · Uses: G001, S010

S012 · implies

Before

ORIGINAL last config=[f18, 3];input length=3;matched prior indices=[0, 2, 2, 3]

After

valid_path=Yes;FULL input consumed=Yes;last final=Yes;accepted=Yes;one successful finite path suffices despite dead branches

Conditions: none

Keep valid separate from accepted:a premature final state does not accept.Only accepted=True gives the finite existential witness for this word,not determinism,totality or DFA equivalence.The tag cannot turn false into true.

Step identifiers and dependencies

Rule: nfa_valid_path_FULL_input_final_existential_acceptance · Uses: G001, S011

Reverse checks

  • 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

([a18, a18, b18], [[s18, 0], [m18, 0], [m18, 1], [m18, 2], [f18, 3]], [0, 2, 2, 3], Yes, Yes, one_finite_path_consuming_full_input_and_ending_final_proves_membership)

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: 734ce28146170be851992003638c3fd4331fe889b8a39248313247d117eccbb8
  • candidate record SHA-256: 5430fd08a520229647e7d08145babb83f256a2335bb5668cc8362ed09f1fb277
  • semantic review receipt SHA-256: 357d7ad7a6726b2a757558d3b9586a408ade06526cc023da093719c292704438
  • question-first witness SHA-256: 99cefe17e98c7a74321801cf72df6d02fc95b6a6b78aa335accb7e11ed467b2a
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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