Reqular Expressions Questions

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61.

Which of the following operation can be applied on regular expressions?

A

Union

B

Concatenation

C

Closure

D

All of these

Correct Answer: D

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62.

The set of all strings over ? = {0,1} in which all strings that beings and ends with 0 is

A

0(0+1)0

B

00

C

00(0+1)0

D

All of these

Correct Answer: A

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63.

The set of all strings over ? = {a,b} in which all strings having bbbb as substring is

A

(a+b)* bbbb (a+b)*

B

(a+b)* bb (a+b)*bb

C

bbbb (a+b)*

D

bb (a+b)*

Correct Answer: A

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64.

The set of all strings over ? ={a,b} in which a single a is followed by any number of b

A

ab* + ba*

B

ab*ba*

C

a*b + b*a

D

None of these

Correct Answer: A

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65.

The set of all strings over ? = {a,b} in which all strings of a

A

ab

B

a*bbb

C

(a+b)* bb

D

All of these

Correct Answer: C

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66.

Which of the following identity is wrong?

A

R + R = R

B

(R*)* = R*

C

?R = R? = R

Correct Answer: D

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67.

Which of the following statement is true?

A

Every language that is defined by regular expression can also be defined by finite automata

B

Every language defined by finite automata can also be defined by regular expression

C

We can convert regular expressions into finite automata

D

All of these

Correct Answer: D

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68.

Which of the following identity is true?

A

? +RR* = R* = ? + R*R

B

(R1R2)*R1 = R1(R2R1)*

C

R*R* = R*

D

All of these

Correct Answer: D

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69.

If P, Q, R are three regular expressions and if P does not contain a then the equation R = R + RP has a unique solution given by

A

R = QP*

B

R = P*Q

C

R = RP

D

None of these

Correct Answer: A

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70.

How many string of length less than 4 contains the language described by the regular expression(x+y)*y(a+ab)*?

A

7

B

10

C

12

D

11

Correct Answer: D

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