Tribhuvan University

Institute of Science and Technology

2080-new

Bachelor Level / second-semester / Science

Computer Science and Information Technology( CSC165 )

Discrete Structure

Full Marks: 60 + 20 + 20

Pass Marks: 24 + 8 + 8

Time: 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.

SECTION A

Attempt any TWO question.

1

How can you use mathematical induction to prove statements? Use mathematical induction to show that sum of first n positive integer is
$$\frac{{n(n + 1)}}{{2}}$$

2

Explain linear homogeneous recurrence relation with constant coefficients. What is the solution of the recurrence relation an = 6an-1 – 9an-2 with initial conditions a0 = 1 and a1 = 6?

3

What is shortest path problem? Use Dijkstra’s shortest path algorithm to find the shorteszt path between vertices a and z in the weighted graph below:

- Hamro CSIT

SECTION B

Attempt any EIGHT question.

4

Let us assume tha R be a relation on the set of ordered pair of positive integers such that ((a, b), (c, d)) ∈ R if and only if ad = bc. Is R an equivalence relation?

5

Define function. Let f1 and f2 be function from R to R such that f1(x) = x2 and f2(x) = x – x2 . What are the functions f1 + f2 and f1 . f2?

6

Explain fuzzy set with example. How do you find complement of a fuzzy set?

7

What is congurent modulo? Determine whether 37 is congurent to 3 modulo 7 and wheather -29 is congurent to 5 modulo 17.

8

Define network flow with example. What are saturated edge, unsaturated edge and slack value?

9

Give an example of tautology and contradiction. Show that implication and contrapositive are equivalence.

10

What is direct proof ? Give a direct proof that if m and n are both perfect squares, then mn is also a perfect square.

11

What is product rule? How many strings are there of four lowercase letters that have the letter x in them?

12

Explain the matrix representation of relations with example.