# Question 23905: A Subset Accepts Exactly When It Intersects the NFA Final Set [Return to catalogue page 120](https://ocme.evemisslab.com/en/questions/page/120/) [← Question derivation index](https://ocme.evemisslab.com/en/questions/) · [Original question batch](https://ocme.evemisslab.com/en/practice/batch-20261014-advance-20261112-r07-subset-construction-nfa-to-dfa-foundations/#q-20261014-advance-20261112-r07-subset-construction-nfa-to-dfa-0055) This teaching derivation has second-context AI mathematical and bilingual semantic review, limited to the model and assumptions stated in this question. It has no human review or new Lean proof and does not promote the original question or MKO to Canonical truth. R0046-23905 · q-20261014-advance-20261112-r07-subset-construction-nfa-to-dfa-0055 ## Original question and givens Use complete epsilon-NFA states=[s4, m4, f4, e14, e24, d4], alphabet=[a4, b4], start=s4, final_states=[f4], transitions=[[s4, null, m4], [s4, null, d4], [m4, a4, m4], [m4, b4, f4], [f4, null, e14], [e14, null, e24]]. Each transition is [from,input symbol or null,to], with null consuming no input. States/labels and transitions must qualify, and subsets are unique carrier subsets sorted lexicographically. Empty alphabet/final sets and empty subset states are allowed. Given subset S=[f4, m4]. Give (subset, NFA_final_states, intersection, accepting_subset, certificate). - G001 — Use complete epsilon-NFA states=[s4, m4, f4, e14, e24, d4], alphabet=[a4, b4], start=s4, final_states=[f4], transitions=[[s4, null, m4], [s4, null, d4], [m4, a4, m4], [m4, b4, f4], [f4, null, e14], [e14, null, e24]]. Each transition is [from,input symbol or null,to], with null consuming no input. States/labels and transitions must qualify, and subsets are unique carrier subsets sorted lexicographically. Empty alphabet/final sets and empty subset states are allowed. Given subset S=[f4, m4]. Give (subset, NFA_final_states, intersection, accepting_subset, 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. - [mko-subset-construction-nfa-to-dfa](https://ocme.evemisslab.com/en/mko/mko-subset-construction-nfa-to-dfa/) ## Step-by-step derivation S001 · impliesBefore source operation=subsetdfa-accepting-subset;original snapshot and mathematics retained After explicit ordered source output fields=[subset, NFA_final_states, intersection, accepting_subset, certificate] Conditions: none Keep the source snapshot while listing ordered fields without JavaScript.Radius uses its original mode to select6 or11 fields without padding;distinguish nonclaims from actual negations. Step identifiers and dependenciesRule: source_ordered_interface_explicit_without_javascript · Uses: G001 S002 · impliesBefore ORIGINAL states=[s4, m4, f4, e14, e24, d4],alphabet=[a4, b4],start=s4;ORIGINAL transition order=[[s4, null, m4], [s4, null, d4], [m4, a4, m4], [m4, b4, f4], [f4, null, e14], [e14, null, e24]] After final set normalized UTF16=[f4];states nonempty,alphabet/finals/relation MAYEMPTY;DUPLICATE triples rejected in THIS model Conditions: none This model differs from the earlier NFA node:transition triples are unique and finals are sorted.Subsets must be actual carrier subsets;do not import old duplicate/final-order conventions. Step identifiers and dependenciesRule: subsetdfa_qualified_NFA_signature_DUPLICATE_edges_REJECTED_here · Uses: G001, S001 S003 · impliesBefore EXACT ORIGINAL supplied S=[f4, m4];normalized SAME-machine final set=[f4] After actual intersection=[f4];accepting_subset=Yes;NO EPS closure inserted Conditions: none This is the definition of an accepting DFA subset,not NFA empty-word acceptance from an arbitrary unclosed S.The empty subset is a legal rejecting dead state. Step identifiers and dependenciesRule: subsetdfa_EXACT_given_subset_final_intersection_NO_hidden_closure · Uses: G001, S002 ## Reverse checks - 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 ([f4, m4], [f4], [f4], Yes, DFA_subset_accepts_exactly_when_it_intersects_the_NFA_final_set) 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: 9db37964dc46e535f5f79aac4df7b81818a0f5d3c0f22b1f3683b5cbfe39d961 - candidate record SHA-256: 601ae1cebc650858c57e81ed567314b2a2b2e75a39455aa23247e3cf78b09a7b - semantic review receipt SHA-256: a7c0d888ade6d307703c4222c4137c78c0d2448babdcba2fa3446fe6fdd343c1 - question-first witness SHA-256: c9571f97a37d503ad6a61034cc00108543a05c37ef246d1c4962f55136a3de02 - Lean: NOT_RUN · human review: NOT_PERFORMED [Same-source full JSON](https://ocme.evemisslab.com/data/question-derivations/questions/q-20261014-advance-20261112-r07-subset-construction-nfa-to-dfa-0055.json)