Entries Tagged 'Fun' ↓

I’ve been grumbling for a while about the lack of spreadsheet choices for the Mac lately. Excel is really nice, but I don’t want/need the whole office suite (plus its not a Universal Binary yet), Appleworks is a joke (and a bad one at that), OO is a system hog (and slow for me), and Numsum just isn’t quite there.

Just when I’m beginning to give serious thought to making my own spreadsheet program, Google releases Google Spreadsheets. I got my invite today and so far I’m liking it. I uploaded my Stargate episode list (to help me keep track of which ones I’ve seen, rating, etc.) and it is working pretty good for me. Only had to change one formula, which is impressive because it just uploaded that Excel file with no other problems.. The only bad thing so far is one spreadsheet I tried to upload just wouldn’t load. But it is a rather large file (about 1.5 Megs of historical stock data on several worksheets).

Its been a while since I posted anything, but rather than just give the usual “Oh, I’m so busy, I’ll write more later” type of post, I thought I would just jot down some little things that I’ve given some thought to recently.

And in the immortal words of Forrest Gump: “That’s all I have to say about that.” Have a great day!

Dr. Dobb’s magazine this month has an article entitled “Sudoku & Graph Theory” which caught my eye. The article describes a logical Sudoku solver the authors built that uses graph theory techniques to analyze the puzzle.

This really got my attention because graph theory is an important field of mathematics that has a number of applications (network traffic flows for example), and it is something that I’m always interested to learn more about.

The first thing the article does is assume the 81 cells of a sudoku puzzle represent a vertex on a graph. They then point out that the numbers that can be assigned to each row, column, or 3×3 square can be thought of as a node of a bipartite graph. That node contains a array of numbers that could possibly be in that position on the puzzle.

This is exactly what I do when trying to solve a sudoku puzzle, but expressed in mathematical/topological terms. (This is what I was trying to get across in my post about Sudoku Strategy.)

The article then goes on to present two methods of logically eliminating number from the array to find the correct answer: Pile Exclusion and Chain Exclusion. Sadly, I can not find any links on the web to explain these algorithms in more detail, but the article does an ok job of showing how they work.

I do want to point out that if you read the full article, beware that the sample sudoku puzzle they present does not seem to match up with the sample arrays (or vectors as they call them) when they are demonstrating the chain and pile exclusions!

My own personal preference seems to be the Pile Exclusion, that seems to match up with how I solve puzzles. It is basically a system where you find groups of numbers that are common across several squares (usually in a 3×3 section, but I often expand it to include the row and column). Usually this works out so that you have two squares where the numbers could be 1,3,7 in one and 1,7 in the other. Then you look at the other squares and if you see that 1 and 7 aren’t a choice in any of them, then 1 and 7 must be in the two squares you are looking at. This means that the 3 is not a possible answer, so you can mark it out. This usually winds up helping you figure out where the 3 is supposed to go.

The Chain Exclusion is similar in that you are looking for groupings of numbers, but with this algorithm you are looking for the numbers to be shared in other parts of the array in order to rule out other locations. For example, if you have 1,3 and 3,4 and 4,1 as the possible answers in three cells, then other locations in the puzzle that contain a 3 can be ruled out. Personally I find the Chain Exclusion method to be more of a leap than the Pile Exclusion.

Both of these methods basically boil down to using logic to reduce (or outright find) the possible numbers that could be the answer. Using both, as the program written for the article does, makes for a powerful set of tools to work your way through the puzzle. The alternative is to do a “brute force search” which means simply trying every possible number in ever possible cell until you get the solution. Since there are 81 cells and 9 possible numbers per cell that means there are 9^81 possible answers (in plain english this means 19 followed by 76 zeros) give or take a few depending how many numbers were already filled in for you. Needless to say, using Pile and Chain Exclusions will help you get the puzzle solved much sooner.

So go check out the article in the Feb 2006 issue of Dr. Dobb’s magazine, it’s a great read.

For the most part, Podcasts don’t do a lot for me. That makes me feel kinda sad because I really like the idea of Podcasting, and I’m already listening to my iPod in the car, so it seems like a natural fit. I’ve only listened to about 4 or 5 podcasts, and with one exception they really haven’t captured me like I thought they would.

The exception is The Escape Pod which is a weekly sci-fi short story podcast. Most of the stories that are read are pretty good, and the host Steve Eley does a good job of presenting the show (and reading/performing the stories). If you are into sci-fi or even just good stories swing by and check them out. I found the podcast through iTunes a while back and its the only podcast I still subscribe to. And after listening to several podcasts back to back, Steve’s suggestion to blog about the Escape Pod finally worked.

I’ve really gotten into the idea of tagging blog posts, it makes your data more accessible to engines like technorati. Plus in the future as more people tag and more engines understand and index the tags its going to be possible to look at pages in a more accurate light, and I think that is exciting.

Along those lines the other day I was wondering how my tags stacked up against what I was writing about. Put simply, according to my banner at the top of the page this blog is about python, games, AI, programming, and other topics. How close to those topics are my postings?

I whipped up python script and had it pour over a backup of my posts (of which there are little over 150). The script basically counted the number of times individual words appeared. My thinking was that the words that show up the most frequently are probably what I’m writing about the most and it would be interesting to see if the matched up with the focus of this site.

Below are some of the top words. The list isn’t complete, but it is some of the more interesting ones and their frequency:

1. 109 - Python
2. 97 - Think
3. 65 - Program (and Programming)
4. 44 - Google
5. 24 - Java
6. 23 - Mac
7. 22 - Games
8. 19 - Tags
9. 13 - Coding
10. 12 - RPG
11. 11 - Motivation
12. 10 - Windows
13. 10 - Wasteland
14. 8 - XEmacs
15. 15 - A9
16. 6 - Dokken
17. 3 - Sudoku

The last item in that lists, Sudoku, really surprises me. I’ve written about it I think twice, yet this month I’ve gotten more hits from search engines on that one word than any other! It accounts for 6.1% of the terms that lead to my site. Crazy….

But back to the list: I was happy to see that Python and other programming related topics were high on the list. That’s why I started this blog, as a place for me to talk turkey about programming in general (and python in particular). For the most part the list I generated fits with what I thought I was writing about which fits with what the site description is, so I guess I’m on target. The only phrase I didn’t really see was GTD or “Getting Things Done” and I think that’s because I usually mention it by the long name, which would get mangled up in this count.

So over all for this experiment, I think my tags are pretty close to the focus of my site. I think the next step would be to look at each post individually and try to determine if the tags I used match the content. But that’s another fun task for another fun day….

I was thinking of doing an article about Sudoko and my strategy for solving them, but a quick check on the MAA.org website lead me to an article which eventually lead me to Sudoku.com where there are several pages of strategy.

I read through them quickly and for the most part that site does what I do to solve them, but it explains it in a weird way (at least that’s what I thought). Maybe this will inspire me to do my own “how to win” page.

UPDATE: I made a page that help you solve sudoku puzzles by giving you hints. Check it out: Sudoku Helper

According to USAToday.com there is a Bigfoot conference going on in Texas this weekend.

Of course, if you had my Sasquatch News Dashboard Widget you’d know about this. Here’s a screen shot of what the news looks like now:

From this article on MSNBC:Space crew weathers a scare during re-entry

When describing to reporters the air leak in his space capsule (for those of you who don’t follow space much, that is a very very very bad thing to have happen) Cosmonaut Sergey Krikalev said:

“In principle this was an anomalous situation of medium complexity. … In fact, it was a fairly serious situation.”

Yikes, in my book any time air is leaking out of my sapceship while it is in space and I am sitting it it, it is an extremely serious situation.

I saw this article about the next “tourist” who is scheduled to visit the international space station. Apparently he wants to do something a little different: Japanese whiz aims for space — in cartoon uniform

As dorky as it might sound right now, that might look pretty cool when they are doing their walk to the launch pad. Two cosmonauts and a guy gressed up like a Gundam pilot.

Of course it would be even cooler if he could actually dress up like the Gundam itself…

The other day my wife was telling me about the sudoku puzzle that they like to do in her office (USAToday is where they get them). I had played with some of these puzzles a year or two ago, so I was anxious to try one out, because they are pretty fun.

Today I was going over to the MAA website and saw there is a nice column about about Sudoku! Check it out:Sudoku Variations.

It talks more about the history and variations of the game than it does about the math aspects of it, but it is still a good read.