Posted by yengiang on Friday, April 22, 2011 at 1:09am.
The sum of the degrees of the 7 vertices add up to an odd number (3+3+4+4+4+5+6=29), which is impossible if there are only 7 vertices (courses).
Is there a typo?
Vertex colour would represent a different exam date, and edges would represent students.
Yes, there's a typo. It's actually 3+4+4+4+4+5+6=30 and there's a graph included in this problem but I don't know how to show the graph so that was why I just described how it looked like with all the vertices and degrees of each. Let me list those vertices and edges:
MCS100 connects to MCS101,110,135.
MCS101 connects to 100,135,130,120.
MCS102 connects to 135,130,120,110.
MCS110 connects to 102,100,135,120.
MCS120 connects to 110,102,101,135,130.
MCS130 connects to 120,102,101,135.
MCS135 connects to 130,120,110,102,101,100.
Thank you.
To solve the colouring problem, there is no systematic way that guarantee results.
However, for simple cases the greedy method usually works.
You can start by assigning two adjacent vertices colour numbers, say
1 to 100, and
2 to 101.
Now observe that 100-101-135 form a triangle, so 135 has to have a third colour, so
3 to 135.
Now check if there are other triangles with 100-101 as a base (none).
Similarly check if there are other triangles that use 100-135 as a base:
100-135-110: so 110 has to be assigned either colour 2 or colour 4.
Continue this by trial and error, you should get the colouring in a couple of tries. If you don't succeed, post.
I've got the colors as they should be, but am unsure how to describe how it will help schedule anything.