2009 UMD Programming Contest - Judges' Notes

Problem A

• Most problems were seen in the 1,000,000 test case.  The judges first looked at this test case before looking any further into other test cases.  Most solutions reported it as having 83337 coins instead of 83335.  Some solutions did not report any output at all for this test case, most likely due to stack overflow.  There was one solution that gave correct answer, but took about 26 seconds to compute it. 
• This problem apparently looked the easiest, as most contestants have tried it, but it turned out to be harder than it looked, as most contestants had troubles with it.

Problem B

• This problem was not supposed to be scary at all (aside from professor Tür, of course!).  Some Number Theory background was assumed.  In particular, that gcd(a,b) * lcm(a,b) = a*b.  Computing gcd(a,b) can typically be found in any good programming book.  The "divides" concept was fairly well explained, although maybe it was too much Math-speak for non-Math majors.

Problem C

• The original cipher was actually given to Dennis by his mom!  It was only slightly modified for the problem.

Problem D

• Khishtaki and Saritanur, who are they?  These names were taken from a Tajik (Persian) children's folk tale.  Here it is, loosely translated, [Khishtaki Saritanur], have a read!

Problem E

• Credit for this one goes to the Evil Judge Luke, who wanted contestants to mis-read the problem and do it the hard way.  Amazingly, most contestants saw through this badness.
• This turned out to be a problem trying to make itself look harder, when it was really easy.  Better luck next time, judges!