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Previous Year Question Paper

CSIT-503 (A) - Theory of Computation

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

• Attempt any five questions.

• All questions carry equal marks.

Q.1
a)Unit 1

Construct a NFA second last symbol is zero over the alphabet (0, 1) than convert in DFA?

b)Unit 1

Design a DFA to accept string of 0's and 1's when interpreted as binary numbers would be multiple of 4.

Q.2
a)Unit 3

Write CFG to accept the language defined by, L{a^i b^j c^k i, j, k, >= 0, i = j + k.

b)Unit 2

Derive Regular Expression from this Finite Automata. alt=''

Q.3
a)Unit 3

How ϵ\epsilon-productions are eliminated from a grammar whose language doesn't have empty string? Remove ϵ\epsilon-productions from the grammar given below. S →\to aA|B|C, A →\to aB|ϵ\epsilon, B →\to Aa, C →\to aCD, D →\to ddd

b)Unit 2

Construct an equivalent FA for the given regular expression (101)(01 + 11)(10 + 10)

Q.4
Unit 3

Consider the following productions, S →\to aB|bA, A →\to aS|bAA|a, B →\to bS|aBB|b For the string aabbabbba, find the:

i) Leftmost derivation

ii) Rightmost derivation

iii) Parse Tree

Q.5
Unit 4

Construct the PDA accepting the language.

i) L={anb2n∣n≥1}L = \{a^n b^{2n} \mid n \ge 1\} by empty stack.

ii) L={wcWR∣w is in (a+b)∗}L = \{wcW^R \mid w \text{ is in } (a+b)^*\} by empty stack.

iii) L={anbc2m∣n≥1}L = \{a^n b^{c2m} \mid n \ge 1\} by empty stack.

Q.6
a)Unit 4

Let G be the grammar given by S →\to aABB/aAA, A →\to aBB/a, B →\to BBB/A construct the PDA that accepts the language generated by this grammar G.

b)Unit 3

Define ambiguous grammar. Show that the following grammar is ambiguous S →\to aSbS | bSaS | ϵ\epsilon

Q.7
a)Unit 5

What is the difference between a recursive and recursively enumerable Languages?

b)Unit 5

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

Q.8
Unit 5

Write a short notes (any three):

i) Decidability

ii) Universal Turing Machine

iii) 2 Way DFA

iv) Petranet Model