Reqular Expressions Questions

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81.

L is a regular Language if and only If the set of __________ classes of IL is finite.

A

Equivalence

B

Reflexive

C

Myhill

D

Nerode

Correct Answer: A

According to Myhill Nerode theorem, the corollary proves the given statement correct for equivalence classes.

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82.

A language can be generated from simple primitive language in a simple way if and only if

A

It is recognized by a device of infinite states

B

It takes no auxiliary memory

C

All of the mentioned

D

None of the mentioned

Correct Answer: B

A language is regular if and only if it can be accepted by a finite automaton. Secondly, It supports no concept of auxiliary memory as it loses the data as soon as the device is shut down.

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83.

Which of the following does not represents the given language?
Language: {0,01}

A

0+01

B

{0} U {01}

C

{0} U {0}{1}

D

{0} ^ {01}

Correct Answer: D

The given option represents {0, 01} in different forms using set operations and Regular Expressions. The operator like ^, v, etc. are logical operation and they form invalid regular expressions when used.

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84.

According to the given language, which among the following expressions does it corresponds to?
Language L={x?{0,1}|x is of length 4 or less}

A

(0+1+0+1+0+1+0+1)⁴

B

(0+1)⁴

C

(01)⁴

D

(0+1+?)⁴

Correct Answer: D

The extended notation would be (0+1)4 but however, we may allow some or all the factors to be ?. Thus ? needs to be included in the given regular expression.

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85.

Which among the following looks similar to the given expression?((0+1). (0+1)) *

A

{x? {0,1} *|x is all binary number with even length}

B

{x? {0,1} |x is all binary number with even length}

C

{x? {0,1} *|x is all binary number with odd length}

D

{x? {0,1} |x is all binary number with odd length}

Correct Answer: A

The given regular expression corresponds to a language of binary strings which is of even length including a length of 0.

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86.

If R represents a regular language, which of the following represents the Venn-diagram most correctly?

A

An Irregular Set

B

R*

C

R complement

D

R reverse

Correct Answer: B

The given diagram represents the Kleene operation over the Regular Language R in which the final states become the initial and the initial state becomes final.

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87.

The given NFA corresponds to which of the following Regular expressions?

A

(0+1) *(00+11) (0+1) *

B

(0+1) *(00+11) *(0+1) *

C

(0+1) *(00+11) (0+1)

D

(0+1) (00+11) (0+1) *

Correct Answer: A

The transition states shown are the result of breaking down the given regular expression in fragments. For dot operation, we change a state, for union (plus) operation, we diverge into two transitions and for Kleene Operation, we apply a loop.

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88.

Concatenation Operation refers to which of the following set operations:

A

Union

B

Dot

C

Kleene

D

Two of the options are correct

Correct Answer: B

Two operands are said to be performing Concatenation operation AB = A

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89.

Concatenation of R with ? outputs:

A

R

B

?

C

R.?

D

None of the mentioned

Correct Answer: B

By distributive property (Regular expression identities), we can prove the given identity to be ?.

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90.

RR* can be expressed in which of the forms:

A

R+

B

R-

C

R+ U R-

D

R

Correct Answer: A

RR*=R+ as R+ means the occurrence to be at least once.

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