第 22447 題：下推自動機

原題與已知條件

transition=[from,input-or-null,required-top,to,replacement-bottom-to-top]的finite nondeterministic PDA。操作=pda-bounded-search-boundary；資料={"states":["push21","pop21","accept21"],"input_alphabet":["a21","b21"],"stack_alphabet":["Z21","A21"],"start_state":"push21","bottom_symbol":"Z21","final_states":["accept21"],"transitions":[["push21","a21","Z21","push21",["Z21","A21"]],["push21","a21","A21","push21",["A21","A21"]],["push21","b21","A21","pop21",[]],["pop21","b21","A21","pop21",[]],["push21",null,"Z21","accept21",["Z21"]],["pop21",null,"Z21","accept21",["Z21"]]],"input":["a21","a21","b21","b21"],"max_steps":1}。請依 exact_ordered_tuple_declared_by_interface 欄序回答。

• G001 — transition=[from,input-or-null,required-top,to,replacement-bottom-to-top]的finite nondeterministic PDA。操作=pda-bounded-search-boundary；資料={"states":["push21","pop21","accept21"],"input_alphabet":["a21","b21"],"stack_alphabet":["Z21","A21"],"start_state":"push21","bottom_symbol":"Z21","final_states":["accept21"],"transitions":[["push21","a21","Z21","push21",["Z21","A21"]],["push21","a21","A21","push21",["A21","A21"]],["push21","b21","A21","pop21",[]],["pop21","b21","A21","pop21",[]],["push21",null,"Z21","accept21",["Z21"]],["pop21",null,"Z21","accept21",["Z21"]]],"input":["a21","a21","b21","b21"],"max_steps":1}。請依 exact_ordered_tuple_declared_by_interface 欄序回答。

定義與適用範圍

沿用原題明示的論域、假設與來源 MKO 定義。本題已完成第二對話數理與中英語義覆核，並由原始參數逐題獨立重算模型、答案與每個算術步驟；原題仍為 candidate。

• mko-pushdown-automaton

逐步推導

source operation=pda-bounded-search-boundary;original snapshot and mathematics retained

explicit ordered source output fields=[input, max_steps, found_accepting_run, rejection_or_nonmembership_claim, boundary]

ORIGINAL transition index=0;[from,input_or_null,required_top,to,replacement_bottom_to_top]=[push21, a21, Z21, push21, [Z21, A21]];bottom=Z21

states/input/stack symbols legal;null input consumes0;top=bottom requires replacement first bottom,otherwise replacement contains NO bottom;ORIGINAL transition position retained

ORIGINAL transition index=1;[from,input_or_null,required_top,to,replacement_bottom_to_top]=[push21, a21, A21, push21, [A21, A21]];bottom=Z21

states/input/stack symbols legal;null input consumes0;top=bottom requires replacement first bottom,otherwise replacement contains NO bottom;ORIGINAL transition position retained

ORIGINAL transition index=2;[from,input_or_null,required_top,to,replacement_bottom_to_top]=[push21, b21, A21, pop21, []];bottom=Z21

states/input/stack symbols legal;null input consumes0;top=bottom requires replacement first bottom,otherwise replacement contains NO bottom;ORIGINAL transition position retained

ORIGINAL transition index=3;[from,input_or_null,required_top,to,replacement_bottom_to_top]=[pop21, b21, A21, pop21, []];bottom=Z21

states/input/stack symbols legal;null input consumes0;top=bottom requires replacement first bottom,otherwise replacement contains NO bottom;ORIGINAL transition position retained

ORIGINAL transition index=4;[from,input_or_null,required_top,to,replacement_bottom_to_top]=[push21, null, Z21, accept21, [Z21]];bottom=Z21

states/input/stack symbols legal;null input consumes0;top=bottom requires replacement first bottom,otherwise replacement contains NO bottom;ORIGINAL transition position retained

ORIGINAL transition index=5;[from,input_or_null,required_top,to,replacement_bottom_to_top]=[pop21, null, Z21, accept21, [Z21]];bottom=Z21

states/input/stack symbols legal;null input consumes0;top=bottom requires replacement first bottom,otherwise replacement contains NO bottom;ORIGINAL transition position retained

PDA complete ORIGINAL transition count := sum(1, 1, 1, 1, 1, 1)

PDA complete ORIGINAL transition count = 6

ORIGINAL states=[push21, pop21, accept21],input alphabet=[a21, b21],stack alphabet=[Z21, A21];start=push21,bottom=Z21,final states=[accept21]

finite unique pairwise-disjoint alphabets qualified;transition count=6;acceptance convention FULL input in final state,NOT empty stack;qualification alone proves NO run,determinism or CFG equivalence

ORIGINAL input=[a21, a21, b21, b21];initial configuration=[push21, 0, [Z21]];max_steps=1;stack cap=7

depth0 fully-consumed final-state acceptance=否;both STEP and STACK limits apply;not an unbounded rejection test

ORIGINAL search depth=0;ALL frontier configs=[[push21, 0, [Z21]]];stack cap=7

ALL [from,ORIGINAL transition index,next_or_null,within_stack_cap,accepts_IN_THIS_SEARCH] rows=[[[push21, 0, [Z21]], 0, [push21, 1, [Z21, A21]], 是, 否], [[push21, 0, [Z21]], 1, null, 否, 否], [[push21, 0, [Z21]], 2, null, 否, 否], [[push21, 0, [Z21]], 3, null, 否, 否], [[push21, 0, [Z21]], 4, [accept21, 0, [Z21]], 是, 否], [[push21, 0, [Z21]], 5, null, 否, 否]];next distinct frontier=[[accept21, 0, [Z21]], [push21, 1, [Z21, A21]]];hit=否

ORIGINAL input=[a21, a21, b21, b21];step bound=1;stack bound=7;found_accepting_run=否

rejection_or_nonmembership_claim fixed No;longer or larger-stack accepting runs have NOT been excluded

逐步反向核對

• S012 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S011 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S010 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S009 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S008 · premise_and_result_audit — 以精確有理數重算 PDA complete ORIGINAL transition count，不以小數近似替代。
• S007 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S006 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S005 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S004 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S003 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S002 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。
• S001 · premise_and_result_audit — 回到原始資料與本步條件核對，不把單向推論誤稱等價。

結論

([a21, a21, b21, b21], 1, 否, 否, bounded_nondeterministic_search_failure_cannot_prove_rejection_or_nonmembership)

依上列完整代值及條件核對得到原題答案；原題編號、格式與狀態保持不變。

本題覆核與來源綁定

覆核日期：2026-10-26

原題、答案、步驟表達式、數值 AST 與既有歷史保持原樣；原來的候選狀態屬於來源歷史，不覆寫為形式化證明。