April 1999
MA214: DISCRETE MATHEMATICS

QUESTION 3

Total Marks: 20 Marks

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GRADE A
Sample student's solutions are indicated in green.
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(a) Show that the graph below does not have an Euler trail.

pic2.gif (2002 bytes)

 

[2]
The graph showing is not an Euler trail because the total edges in the graph is an odd number. Besides that, the graph consists of a pair of vertex which have odd number of degrees.

 

(b) Find the adjacency matrices for the following directed graphs.

pic3.gif (2977 bytes)

 

[6]
pic10.gif (3338 bytes)

 

(c) Construct directed graphs that have the following adjacency matrices:
(i)

pic4.gif (886 bytes)

[3]
(ii)

pic5.gif (846 bytes)

 

 

[3]
(i)

pic11.gif (9869 bytes)

 

(ii)

pic12.gif (6487 bytes)

(d) Determine whether or not the graphs G and G' below are isomorphic.

pic6.gif (3479 bytes)

 

If they are isomorphic, give functions g: V(G) ® V(G') and h: E(G) ® E(G') that define the isomorphism. If they are not, give an isomorphic invariant which they do not share.

[6]
The graphs are isomorphic.
h
e1 ® f1
g e2 ® f2
v1 ® w3 e3 ® f3
v2 ® w1 e4 ® f4
v3 ® w2 e5 ® f5
v4 ® w4 e6 ® f6