Q. Consider the following types of languages:

L1 Regular,
L2: Context-free,
L3: Recursive,
L4: Recursively enumerable.

Which of the following is/are TRUE?

I. L3' U L4 is recursively enumerable
II. L2 U L3 is recursive
III. L1* U L2 is context-free
IV. L1 U L2' is context-free

View solution

Q. Which of the following are decidable?

I. Whether the intersection of two regular languages is infinite
II. Whether a given context-free language is regular
III. Whether two push-down automata accept the same language
IV. Whether a given grammar is context-free

View solution

Q. Which of the following problems is undecidable?

View solution

Q. Let < M > be the encoding of a Turing machine as a string over {0, 1}. Let L = { < M > |M is a Turing machine that accepts a string of length 2014 }. Then, L is

View solution

Q. Which of the following problems is undecidable?

View solution

Q. Consider three decision problems P1, P2 and P3. It is known that P1 is decidable and P2 is undecidable. Which one of the following is TRUE?

View solution

Q. Consider the following statements:

1. The complement of every Turning decidable
language is Turning decidable
2. There exists some language which is in NP
but is not Turing decidable
3. If L is a language in NP, L is Turing decidable

Which of the above statements is/are True?

View solution

Q. Let L={w ∈ (0 + 1)*|w has even number of 1s}, i.e. L is the set of all bit strings with even number of 1s. Which one of the regular expression below represents L?

View solution

Q. Let P be a regular language and Q be context-free language such that Q ⊆ P. (For example, let P be the language represented by the regular expression p*q* and Q be {p^nq^n|n ∈ N}). Then which of the following is ALWAYS regular?

View solution

Q. Consider the language L1,L2,L3 as given below.

L1={0^p1^q | p,q ∈ N}
L2={0^p1^q| p,q ∈ N and p=q}
L3={0^p1^q0^r | p,q,r ∈N and p=q=r}
Which of the following statements is NOT TRUE?

View solution

Q. Definition of a language L with alphabet {a} is given as following. L= { a^(nk) | k > 0, and n is a positive integer constant}. What is the minimum number of states needed in a DFA to recognize L?

View solution

Q. Which of the following pairs have DIFFERENT expressive power?

View solution

Q. Which of the following problems are decidable?

1) Does a given program ever produce an output?
2) If L is a context-free language, then is L’ (complement of L) also context-free?
3) If L is a regular language, then is L’ also regular?
4) If L is a recursive language, then, is L’ also recursive?

View solution

Q. Let S and T be language over ={a,b} represented by the regular expressions (a+b*)* and (a+b)*, respectively. Which of the following is true?

View solution

Q. Let L denotes the language generated by the grammar S – OSO/00. Which of the following is true ?

View solution

Q. Consider the following two statements:

S1: { 0^2n |n >= l} is a regular language
S2: { 0^m 0^n 0^(m+n) l m >= 1 and n >= 2} is a regular language

Which of the following statements is correct?

View solution

Q. Given an arbitrary non-deterministic finite automaton (NFA) with N states, the maximum number of states in an equivalent minimized DFA is at least

View solution