Australia made 434 for 4 in their one day cricket match against South Africa (a world record by a huge margin) and then they lost the match by one wicket and one ball!!!. This is simply incredible.

A couple of people suggested that I might like Sudoku and although I tried it out a couple of times before I never really had the patience to finish it. You just have to complete the grid with numbers so that every column, row and 3×3 square contains the numbers 1-9 exactly once. The WSJ had an article today about how the Sudoku crazy is getting out of hand…

British Airways recently issued a memo to its 13,000 cabin crew members reminding them that working on games like the popular Japanese number puzzle during takeoff and landing is prohibited for safety reasons. BA said the move was prompted by passenger concerns that crew members were doing puzzles.

They also published a sample puzzle of medium difficulty which I was motivated enough to actually complete in about 30 minutes. Marco suggested that I try one of the Guardian’s Sudoku’s puzzles which are created by a Sudoku grand master instead of a computer program and I tried my hand at the difficult Feb 6th puzzle. I spent an hour on it before losing patience and giving up.

I was thinking about how to solve Sudoku puzzles by computer and realised that it was quite easy to brute force a solution. Here is a link to a nice website which has a solver and a discussion of the logic behind it. Then I started wondering about how Sudoku puzzles were created to ensure that they had a unique solution. This seems like a more interesting problem to think about. You can make the grid into a graph and the problem is equivalent to finding a proper 9-colouring of the graph given a partial 9-colouring. I am sure Hemanshu will have several interesting things to say about this when I meet him in Champaign this weekend.

I don’t know why I get addicted to some types of puzzles and I am cool to others. I really got addicted to Freecell, but I didn’t like Sokoban very much (even in Nethack I tried to cheat as much as my luck would allow it). Even though some Sudoku games are challenging, somehow I don’t think I will get addicted to them.

Ps. If you want some challenging Freecell games, take a look at this link. There are some very interesting graph theory problems related to Freecell also.

Why is Tetris so addictive? It is like an electronic drug – a “pharmatronic” according to Wired. Studies have shown that playing tetris increases the consumption rate of glucose in the brain giving a slight high. However after 4 to 8 weeks of playing tetris daily, the brain seems to get more efficient and the consumption rate of glucose drops down to normal levels while the score increases seven-fold on an average. Pokhilko, the psychologist who seemed to need treatment himself had this to say about the game

The main part is visual insight. You make your visual decision and it happens almost immediately. Insight means emotion: small, but many of them, every two, three seconds. The second mechanism is unfinished action. Tetris has many unfinished actions [that] force you to continue and make it very addictive. The third is automatization: in a couple of hours, the activity becomes automatic, a habit, a motivation to repeat.

Unfinished actions means that you can change your mind about your decisions upto the very last millisecond.

I started playing this so much that every time I closed my eyes I would see images of blocks falling and put into place. Studies have also been done to show how tetris dreams help in learning to play the game. Considering the amount that I sleep, I should be better than the qow. However, maybe it is the cataloging of those dreams (which I do not do) that are important. Hmm. Tetris taxonomy is going to be useful while sledging in the two player version of the game.

The game is inherently quite evil, because even if you play perfectly, you are destined to lose almost all the time. Several optimization problems in tetris have been shown to be NP-complete making it hard to devise a good algorithm to play the game. Heidi Burgiel has explained that if you only get alternating S’s and Z’s (also known as left snake and right snake) then you are going to lose the game in less than 70,000 moves. If that is not evil enough for you there is also Bastard Tetris (installed in /zz/pub) where the game shows you the best piece and then give you the worst possible piece.