Sudoku

February 9th, 2006
Sudoku

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.

wordpress

February 1st, 2006

powered by wordpress

I finally upgraded wordpress (this blogging software) to version 2.0.1 and beyond. Instead of following the usual upgrade instructions, I just checked out an svn version right on top of my old wordpress directory. I had to move things around a bit, but eventually I have this blog running on a development version that I can keep up2date whenever I want to.

Now I have to figure out how to get my “I’m feeling lucky plugin” working again and update it on the wordpress plugin repository. Also, the backup plugin needs some tweaking. I shall also tweak the template to give my del.icio.us bookmarks a little more space. I seem to be bookmarking more things and easing up on writing blog posts. If you notice anything funny with the website after the upgrade, please let me know.

aaaahhhhhhh!!

January 22nd, 2006

(via Chris) This page plots the number of results obtained from google for words of the form a{n}h{m} and then colours it using the log of that value. The shortest word of this form that doesn’t appear in google’s result is
aaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
it has 18 a’s and 50 h’s, but of course once google indexes these pages we will get a new minimum.

What is interesting is that when writing a{n}h{m}, people tend to use more h’s than a’s. Does this mean that they were more surprised or more satisfied?

Webcams

January 9th, 2006

Uchicago Magazine has some cool full motion video webcams courtesy of NSIT. Check them out….

Beer Pipeline

January 3rd, 2006

While reading about Oil Pipelines in wikipedia, I came across a mention of a Beer Pipeline.

Bars in the Veltins-Arena, a major football ground in Gelsenkirchen, Germany, are interconnected by a 5 km long beer pipeline. It is the favourite method for distributing beer in such large stadiums, because the bars have to overcome big differences between demands during various stages of a match; this allows them to be supplied by a central tank.

I refused to believe this untill I saw a BBC article on the AufSchalke Arena that confirmed it.

In fact what was known as AufSchalke Arena in 2001 is now known as the Veltins-Arena after the naming rights were sold to the German brewery.

Germans sure know how to take the beer seriously…

Compiling OpenOffice

January 2nd, 2006

I decided to upgrade to OpenOffice version 2 as I wanted to use oodraw to make some flowcharts. Emerging software on gentoo involves compiling it (though you can install binary package s if you really want) and OpenOffice weighs in at a hefty 150MB download. I think it will only finish compiling tomorrow morning. Meanwhile it does its best to entertain you

Use gcc33: ”
ccache: no
icecream: no
Checking for source packages in /usr/portage/distfiles
Looking for OOO_2_0_0-core.tar.bz2 … ok
Unpacking OO.o build tree – [ go make some tea ] …

After telling me it is not going to use icecream and giving me some time to make some tea it tells me…

Fixing unfortunate snafus

Thats good to know. I wouldn’t want to wake up in the morning to unfortunate snafus.

Ps. Happy New Year everyone.

Updated to Add: It is 11 in the morning now. Still compiling….. :)

Dupes

December 7th, 2005

One advantage of having a web based aggregator that constantly pings away at sites (albiet very politely), is that you get to catch mistakes that feed publishers make. Notice any difference in these two items from Slashdot?.

Slashdot dupes

Click the image for a close look…. I guess Slashdot is worried about getting sued by Microsoft :) ….

Misc links

December 4th, 2005

Update: This is my 101′st post.

Books

November 30th, 2005

I gave up midway on A feast for Crows and started reading Sundiver by David Brin. Time to make a trip down to the Library to pick up some books for the winter break. Any recommendations?

Fires on campus

November 19th, 2005

It looks they finally caught the person who has been setting fires on campus.