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Previous Year Question Paper

CSIT-503 (A) - Theory of Computation

December 2025•CSIT•SEMESTER-5
December 2025
Max Marks: 70
Duration: 3 Hours
Instructions:

• Attempt any five questions.

• All questions carry equal marks.

Q.1
a)Unit 1

Design an NFA for the language L = { w | w contains substring 101 }.

b)Unit 2

Compute the Regular Expression for the DFA as shown below alt=''

Q.2
a)Unit 2

Find a regular grammar that generates the language on {a, b} consisting of all strings with exactly one a's and no more than two b's.

b)Unit 2

State and prove Arden's Theorem. Use it to find the regular expression for a Finite Automaton where the transition system involves multiple state equations.

Q.3
a)Unit 3

Obtain a grammar in Chomsky Normal Form (CNF) equivalent to the grammar G with productions P given below: S \to aAbB A \to aA | a B \to bb | b

b)Unit 3

Obtain a CFG that generates the language L={aibjckmidi,j,kge0textandeitheri=jtextorj=k}L = \{a^i b^j c^k \\mid i, j, k \\ge 0 \\text{ and either } i=j \\text{ or } j=k \}. Is the grammar you have generated ambiguous?

Q.4
a)Unit 4

Construct a PDA accepting {anbnammidm,nge1}\{a^n b^n a^m \\mid m, n \\ge 1\} by final state.

b)Unit 4

Define a deterministic PDA. How a DPDA differ from a non- deterministic PDA?

Q.5
a)Unit 5

Construct Turing Machine (TM) to accept the language L={02n1n22nmidnge0}L = \{0^{2n} 1^n 2^{2n} \\mid n \\ge 0\} over the alphabet, Sigma={0,1,2}\\Sigma = \{0, 1, 2\}.

b)Unit 5

What is NP-complete and NP-hard problems? Explain with examples.

Q.6
a)Unit 1

Determine the DFA that will accept those words from S={a,b}S = \{a, b\} where the number of b's is divisible by three. Sketch the state table diagram of the finite Automaton M also. alt=''

b)Unit 3

Given grammar G with productions S \to aB | bA A \to aS | bAA B \to bS | aBB For the string aaabbabbba, find a rightmost derivation, leftmost derivation and parse tree alt=''

Q.7
a)Unit 1

Determine a NFA accepting {ab, ba} and use it to find a DFA accepting it.

b)Unit 2

Give Regular expressions for the following on Sigma={a,b,c}\\Sigma = \{a, b, c\} (a) all strings containing exactly one a (b) all strings containing no more than three a's (c) all strings which contain at least one occurrence of each symbol in Sigma\\Sigma.

Q.8
a)Unit 3

State and prove Greibach normal Form

b)Unit 5

Turing machine

c)Unit 5

Difference between a recursive and recursively enumerable languages

d)Unit 5

Halting problem