All entries for May 2005

May 31, 2005

Sudoko Problem SOLVED!

Follow-up to Unsolved Problems In Mathematics #2242 : The Secret of Sudoku from The Militant Wing of Pacifism

Well, the number of solutions problem has been solved. I can't claim any credit, of course, but plenty of kudos for this Felgenhauer guy.

The number of valid Sudoku solution grids for the standard 99 grid with 33 regions was calculated by Bertram Felgenhauer to be 6,670,903,752,021,072,936,960 This number is equivalent to 9! 722 27 27,704,267,971, the last factor of which is prime.

Still awaiting confirmation, of course, but it seems pretty sound.

The mechanics of the solution isn't terribly technical, though. Basically, it's a brute force search by computer for unique solutions, which we then multiply by the appropiate number of symmetries. (From above, 27,704,267,971 are the unique solutions, and the rest we multiply by are symmetries.)

The code used is available here. It's in C++ and python, so you should be able to test it yourself. The solution was found based on discussions on an internet forum, so obviously these things are useful, after all!

The minimum givens problem is still open, though.

May 28, 2005

Another random puzzle

Writing about Random puzzle from El Meu Blog

Like before, we want to get from dot to dot.

But this time, we want to go between the dots and minimise time. We assume that we travel through the orange area with unit speed, but that we can also travel through the white area with a speed k. So, how does the optimum route change as k changes?

Environmentally Friendly For Free

It seems that being environmentally friendly always has a cost. There's the fun way, the convenient way, and the environmentally friendly way. Well, not neccessarily… Here's a list of some ways you can benefit the environment, at no cost to yourself.

1. Don't use plastic/paper disposable cups. It is really kinda questionable why people would want to use them. Habit, I suppose. While it is true that most of these cups can be recycled, nowadays, recycling is still inefficient. It costs energy, and itself pollutes. While recycling is better than disposing, it is much worse that using reuseable cups, whose production costs have already been paid.

2. Reduce plastic bag usage. If you are only going a short distance, and you only have a few, large items (like a pizza, for example, or a few bottles), there is no point in getting a plastic bag. So, well, don't. If you are already carrying a bag for your books, then you can put groceries in that as well. You can also re-use plastic bags as bin bags, or for when you go shopping.

3. Store scrap paper. A piece of paper has two sides. For stuff where presentation doesn't matter – like rough, working out paper – use both sides. This will save you money, as well. If you only use one side, then keep it around for the next time you need some paper. When you are printing stuff off, take some of the discarded cover pages, for use as scrap. And when you have used both sides, then remember to recycle!

4. Turn stuff off. When you leave a room, it costs you no time to turn off the lights. When you leave a computer, turn off the monitor. (Standby mode still consumes some power, and also takes time to trigger.) Note though – this depends on whether you are going to leave for a long time or not. If you are just going to be out for a second, then don't bother. The on-off cycle itself costs energy.

5. Buy stuff on special offer. I mean, think about it? Why are they on special offer? Often, it's because the supermarket is trying to offload stuff. And if they don't offload it, it just gets wasted. Don't feel guilty about being a bargain hunter.

6. Don't switch cars. Suppose you've been convinced of the threat posed by Global Warming. Suppose you now view your dirty old vehicle with guilt… Don't just buy a new one. Remember, the construction of cars is itself hugely polluting. As is its eventual disposal. You need to balance out the incremental improvement in efficiency with the one-time cost. If you are going to buy a new car, then sell your old car second hand (if it isn't too horrible), and get a new, cleaner one.

7. Be lazy. Lazy is good. When you are asleep, you consume very little energy. So, oversleep whenever you can. This should not be difficult.

I'll add more when I can think of it.

Fleep, the comic

Writing about web page

Jason Shiga majored in Maths. So, kids, you might see this as a sort of inspiration about what to do with your maths degree. I mean, how to be rich and successful and stuff.

Jason Shiga now works in a library. Ok, scratch that about inspiration…

But Shiga does make good comics. As for his maths past, it certainly shows in some of his work.

Like Fleep, for example

Fleep about a guy who gets trapped in a phone booth. A phone booth, that has suddenly and inexplicably become surrounded by concrete. All the words around him appear to have turned to gibberish, and all he has with him are the phone, a phonebook he can't read, a few coins, a pen, a book in Russian, and a note which he also can't read. Plus, he's running out of air.

He's also extremely smart. Can he escape? Can he figure out how he got trapped in the first place? Well, to say any more would be to spoil things.

Go. Read. Now.

May 22, 2005

Murder, he wrote

Writing about web page

OK, I lied about being dead. Being dead helps me in my skulking-around-activities, so I can work on Project-Eliminate-My-Enemies. It's not like anyone even cared. Bastards.

But, ok, forgive me for the divergence.

Possibly the creepiest thing ever

A doomed Queens man's chilling computer entry led cops to a suspect who allegedly robbed and killed the victim and his sister to finance a return to China, police said yesterday.

So, this guy gets murdered. They catch the murderer, because just before that, he posted a blog entry wondering about his sister's weird boyfriend, who is hanging around his flat for apparently no reason. A short while after he posts his last entry, the boyfriend ties him up, and when he can't find any money, he stabs Simon Ng repeatedly in the chest. And then, a while later, Simon's sister Sharon comes back, and gets stabbed as well.

And the Blog is still up. Really, you can read it here.

And when you read it, it strikes you that the whole thing is completely normal. It's just the blog of a random, mundane, person. Half the articles are on stuff like I'm doing badly on on Japanese class, or about how much hard work it is to clean up. Stuff that we students can all connect to. And then, that final entry.

Today I missed my Japanese class again, since I have gotten a bad throat. I only went to the class once this week, so I am probably so far behind now. I will catch up in the summer tho so no worries hehe. Anyway today has been weird, at 3 some guy ringed the bell. I went down and recognized it was my sister's former boyfriend. He told me he wants to get his fishing poles back. I told him to wait downstair while I get them for him. While I was searching them, he is already in the house. He is still here right now, smoking, walking all around the house with his shoes on which btw I just washed the floor 2 days ago! Hopefully he will leave soon, oh yeah working on the jap report as we speak!

Just non-commital. Just another day. Worrying about homework. Concerned more about his floor, than feeling threatened.

And then he dies.

May 18, 2005

Zhou has Died

Follow-up to Zhou is Still Dying from The Militant Wing of Pacifism

You gotta admire these itsy bitsy viruses. Pluck, courage, and everything. Here's to their ultimate victory over the human race!

Also, they are easier to draw than people.

May 17, 2005

The Eviler Secret of Sudoku

Follow-up to Unsolved Problems In Mathematics #2242 : The Secret of Sudoku from The Militant Wing of Pacifism

Hmm, disease leads to well, diseased thoughts.

Pondering the Guardian's claim to have magically superior Sudoku puzzles 'hand crafted in Japan', I came up with this:

The Price of Sudoku:

Hope you liked it.

Zhou is Still Dying

Follow-up to Zhou is Dying from The Militant Wing of Pacifism

Bob here.

I think we may be approaching the end. He keeps murmuring how I am just a 'figment of his imagination.' Obviously, he is losing touch with reality – mentally, not just politically and ethically.

Some people offered to pray for his better health. I told him that was pointless, since this blog owner is hated by god, since only people hated by god get ill. Besides, he's obviously going to hell. They should pray that he gets sent to the very painful part of hell, and not the very very painful part. Because that would be cruel.

That gets me thinking, though. Maybe I can make money out of this. It will be going to a very good and worthy cause…


May 16, 2005

Hatred, pure hatred

Writing about What lies behind your eyes? from Where the Mind roams free but the Heart stays true

Bob here. Zhou still isn't dead. Damn.Great!

Now, let me vent my insensitive spleen.

To the people who post all those poll results on their blogs:


Really, quit it. You are pushing people who actually produce their own content for their own blogs off the 'Latest Entries Page'. You are wasting server space with stupid copy and pastes when anyone who has enough fingers to click on a link can find out for themselves. You are making a fool of yourself.

I mean, think on it. What's the point? What are you saying to the big wide world here? That you can use google to find a bunch of quiz links? That your entire personality can be encompassed in a group of pointless stereotypes? That you are so scared of speaking for yourself, that you decide to let people judge you due to the arbitary, meaningless whims of a mindless cgi server side script?

You may be a beautiful butterfly. You may be a simple princess. But you are perverting the point of weblogs and making a bad impression of yourself, and that's a fact.

Thank you for reading.

May 2005

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