TopCoder - Open Qualification Round

Well I’m not going to get into the Elimination Rounds.
I was assigned VideoEncode and GridGame.

I spent ~30 minutes of my 60 solving a problem that was really just a bit of algebra. I solved it using binary search, when I just need to rearrange the variables to get a single line piece of code. I had the feeling this was the case, but the stress of the situation I was not trusting myself to solve the algebra faster than getting the binary search working. Net time I’ll have a better indicator. The binary search was required in the AutoLoan problem due to the value been search for had a compounding affect on the result. Whereas here there was no complex relationship.

The second problem was a simple min/max tree problem. Given a 4x4 board how many of the available moves will “win” if I only play perfectly. I had missed the guarantee you win and assuming you play perfectly bits. Not that I know how to solve this. But I went down the path of how many of the moves could I win.

So now I’ll stop trying the path of logic I had been working on after the event, and workout how to solve the problem correctly.

[Some time later]

Oh my, it really was quite simple once I stopped and thought about that at each turn the two players are trying to achieve different things. For our turn we just need to find one move that we win. For the opposition move they win if they find a path we don’t win. So simple now I understand what I was trying to achieve. Other the feeling silly for not know how to program this I now feel relax I worked out how to-do it.

I’ll be ready for next time.

[Just before publishing]

Well the results are in. I came 300th out of 374 in my problem set. Most those people came 317th equal for no score. This hammered my ranking, and I’m now down to 1050. Oh well, I surely can’t get much worse than this.