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東京大学 情報理工学系研究科 コンピュータ科学専攻 2016年2月実施 問題2

Author

kainoj

Description

Let us consider nondeterministic finite automata with -transitions (-NFAs) over the alphabet . An -NFA is an NFA that can additionally have "silent" transitions labeled with a fresh symbol . A word is accepted by an -NFA if there exists a word such that:

  1. is accepted by (when is considered an NFA over the alphabet ); and
  2. removing all the occurrences of in gives rise to .

The language of an -NFA is the set of words accepted by .

An example of an -NFA is given below; it is referred to as . Here is an initial state and is an accepting state.

Answer the following questions:

(1) Give a regular expression that designates the language of the above -NFA .

(2) Give an NFA over such that: ; and is -free, that is, there are no transitions labeled with \varepsilon in .

(3) Give an -NFA such that

Your answer may be -free.

(4) Give an -NFA such that , where is from Question (3). Your answer may be -free.

(5) Give an -NFA such that , where is from Question (3). Your answer may be -free.

Kai

(1)

(2)

(3)

(4)

(5)

contains and is of form of .