Tribhuvan University
Bachelor of Science in Computer Science and Information Technology
Semester 4 · TU Board 2080 (new course)
Course Title: Theory of Computation (CSC262)
Full Marks: 60Pass Marks: 24Time: 3 hours
Candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicate full marks.
Group A
Attempt any TWO question.(2 × 10 = 20)
- 1.10
Describe the extended transition function of NFA. Construct a NFA, using transition table and transition diagram , over {0, 1} that accept the string having substring 01 and ends with 1. Show the acceptance of 0111.
- 2.10
Define CFG. Construct a CFG that generates the language of all palindromes over {a,b} that do not contain the substring aa. Show the leftmost derevation and construct the equivalent parse tree for string babbbab.
- 3.10
How Turing Machine is used as a computing function? Construct a TM for simulating a function f(x) = 2x for x = {1}. Itetrate the TM for input 11 and generate the output 1111.
Group B
Attempt any EIGHT question.(8 × 5 = 40)
- 4.5
Differentiate Kleen closure from positive closure. Compute positive and Kleen closure of {ab}.
- 5.5
Design a Melay machine over {a, b} that generates output 'A' if the input string ends with aa else output 'B' if the string ends with bb.
- 6.5
Construct regular expression over {1,2,….9} that represents
- strings of even numbers with length 4 starting with 2 and ending with 8.
- strings starting with odd numbers and ending with even numbers.
- 7.5
Prove that th language L ={a^n b^n c^n | n≥0} is not a context free grammar.
- 8.5
Construct a PDA that accepts string over Σ ={a,b} that contains equal number of a's followed by equal number of b's. Show acceptance of aabb and aab.
- 9.5
Describe how multi-stack TM is different from the semi-infinite tape TM?
- 10.5
What is intractability? Define time and space complexity of turing machine.
- 11.5
How conversion of PDA to CFG done ? Illustrate with example.
- 12.5
State Arden's theorem. Convert following DFA into its regular expression using Arden theorem.
[figure in the original paper]
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