It was the Indian Express-
Dengue strikes, the latest victim: a doc from AIIMS, Delhi.
7/11 blasts: 7 Indians and 11 Pakistanis involved in the conspiracy.
And bla bla blahhh!

I went on to page 4 of the Pune Newsline… It’s the page which offers you some entertainment. Not really entertainment, ‘TP’ is the right word for it. It has all those cartoon strips, cross word puzzles, daily horoscope and another new Sudoku!

Damn! How much more time am I going to waste on these sudokus? I should not allow myself to become a victim of this cosmic plan of time waste which gives a false satisfaction of having a sharp working brain. I must do something!

Hmmm…

I shall write to the editor of the newspaper explaining how dangerous the idea of solving a sudoku is! How much more productive the nation would become if they stop printing those 9×9 vicious monsters which are so tempting to indulge with and have the gravity to sink-in all your brain power for at-least 15 minutes every day. We can save (15 minutes x 365 days) 5475 minutes per year per person, which is approximately 12 working days! This is a serious brain drain problem our nation is facing today. But no one is even aware of it! I shall make protests in front of the parliament; go on indefinite hunger strike till they ban printing those sudokus in newspapers. They will put me in jail…

JAIL??? Naaaaaaaa!
Okay, forget it! Let me think of something else…
How about writing a “C-program” to solve a sudoku? Just enter the sudoku and get the solution printed on the screen on a single press of the ‘Enter’ key! Sounds good huh?
I got working on this plan. My only comrades were a blank paper and a pencil. I must figure out the algorithm first, before I start implementing the program itself. I knew the algorithm has to use a backtracking strategy.

Now, what the hell is BACKTRACKING? Well… actually… it’s quite simple… it’s like… you know… got it? No??

Ok, let’s make a bollywood style movie story to understand backtracking, if at all you are interested.
The name of the movie would be –“Backtracking se pyar tak!”. Hold on your breath, the most romantic, sci-fi blockbuster of the decade is here – LIGHTS… CAMERA… ACTION!!!

There’s a sweet, pretty girl Preity who travels daily by bus to college. And there is this so-so looking but intelligent boy Rahul from her class who also travels by the same bus. Ohh my god! What a coincidence! So but naturally Rahul likes Preity and is desperate to get into conversation with her. Now Rahul is an intelligent guy as I said before, and he knows that 1st impression matters a lot. He also knows that sense of humor is one of things that girls look for in guys (I am not an expert in these things you know… But let’s move on with this assumption). And you know what? Rahul has built a time machine…Voila!!!

After weeks of sleepless nights and some discussions with his experienced friends, Rahul short-lists 4 great ways of striking conversation with Preity. All these 4 ways might make the pretty girl laugh and she might end up loving Rahul. But there’s a problem… A twist in the tale… Preity is too moody and has 5 different moods on 5 different weekdays. Ohh poor Rahul! How would he figure out which way of striking conversation (out of the 4) will work on which moods of Preity (out of the 5)?

Rahul is the “hero” of our story. How can he fail? On one Sunday he decides to use his time machine to solve this problem. He would go forward in future to the mornings of each day of the next week (to find Preity in a particular mood on a particular morning) and then on every such day he would try his 4 tricks. So for example- Rahul goes to Monday morning and tries trick-1. If it doesn’t work he will come back (backtrack) to Monday morning, 1 step behind, and will try trick-2 and so on till trick-4. If on Monday none of the 4 tricks work, he would come back (backtrack) 2 steps to Sunday where he started with. Now, from here he will go to Tuesday and try the 4 tricks one-by-one as he tried on Monday. He will repeat this until a trick works on Preity successfully. Then he would note down the Day and the Trick number on a piece of paper before he returns to the present from future. This piece of paper will act as the key to success for Rahul’s 1st impression on Preity.

So, will Rahul get the key to success? Would Preity fell in love with Rahul? To know what happens, please visit your nearest Cinema Multiplex to watch – “Backtracking se pyar tak”. (See the poster of the movie-cum-solution space tree below)Hushhhh! So that is how backtracking works! Don’t kill me if you didn’t like the story very much. Wait! What about the time machine? Do you mean to say backtracking programs use time machine to go back and forth in time? Hmm.. That’s one interesting point. Actually, the recursive function in a backtracking program acts as a time machine which moves the context of the program forward and backward.

Thus, I finally opened my VC editor and implemented the sudoku program as a console based application. The first time I ran this program, it looked like this:

The 9 columns of printed values kept oozing out of the screen’s bottom, shooting up into the free space. It reminded me of the Matrix movie. Beautiful! Isn’t it?

Every recursive call to the function ‘Place’ was printing the whole sudoku. 5 minutes were over and still the program was running. The CPU constantly kept on clocking 100% utilization. I opened the CPU cabinet to allow the choking CPU get some oxygen. It was all because of a misplaced call to the ‘PrintResult’ function. I kept on taking screen shots and pasting them in paint to verify that the program is working correctly and not gone into an infinite loop.

You think I am CRAZY! Right? I should have stopped that running program right at the beginning and should have run it again after commenting out the wrong call to ‘PrintResult’. Nopp! You don’t kill a program like that in its 1st run. A lot of emotions are attached to it!

It was only after a few minutes the screen stopped rolling. And the once monstrous looking sudoku was on its knees. It was party time! So, with this program running correctly, I am going to save 5475 minutes per year. A 12 day vacation! How about a trek to Himalayas for this year?

Find my sudoku program here and its ‘exe’ for windows here.
Disclaimer: The program has done no error checking for wrong inputs and the user will solely be responsible for the disastrous outcomes in such cases. It might end up blowing up your machine :P Good Luck!

PS: Sudoku is an NP-complete problem and the approach I have used here is a brute-force approach. Brute-force basically means trying all possible permutations till you reach the solution. It’s like trying all possible combinations of a number-lock till you find the correct combination to open it. Anyway, I am not an expert in algorithms or complexity theory, but if you are interested you can find out various approaches to solve this problem discussed here.

Anyway, I thought it is time to post something on my blog and save it from dying. So here I am, posting an article that I had written back in 2006, Backtracking Se Pyaar Tak!

Let me start this blog post by asking you a simple question.

Who is your principal source of information?

Where do you get to know the things that matter most to you? OR, Where do you get the information that actually influences your decisions regarding your day-to-day life?

It could be as simple as watching a movie or not, deciding a restaurant to have a weekend dinner, finalizing a holiday destination, finding the best/shortest route to a place. Or it could be as crucial as investing your hard-earned money for maximum gains and security, places to buy stuff to get best deals so that you can save a lot, or may be deciding a prospective school for your kids.

Think about this for a minute…

Are most of your answers one of these?

Group1: Books, Newspapers, TV/radio broadcasts, Internet Search (Google, Bing, Yahoo, heard of Wolfram?), Online News Feeds, Advertisements, Online Forums, Emails, Blogs, Twitter, Facebook, Orkut, MySpace.

OR Are they one of these?

Group2: Friends, Roommates, Office Colleagues, Dad, Mom, Girlfriend/Boyfriend, Spouse, Siblings, Relatives, Neighbors, Teachers, Business Partners, Experts (tax consultants, lawyers, doctors etc).

I hope you are getting my point…

People are the prime source of information!

Someone might argue, “But we get to know a lot of interesting/important stuff through Group1, isn’t it?”

I would say yes, but Group 1 is not the prime source of information. These are mere tools/instruments to get the information which is generated by the prime source: People!

Makes sense? Want me to prove it? Ok, tell me how did you get to know about Facebook or Twitter, the hottest social media applications today? The answer by most of you would be: “Through friends”.  Right? That in a way proves it… The prime source of information are the people around us. And that is one more reason why we should make more friends :)

The tools in Group1 provide a great platform for people to share, communicate and interact. I am in no way demeaning their importance.  In fact it humbles me and increases my respect towards these applications when I get to know about news like these: Father delivers baby with youtube’s help!

Social Search

Wouldn’t it be best if you could surround yourself with honest and selfless experts from all possible fields who could guide you through all dilemmas of your life? Honest for obvious reasons and selfless so that you could get their advice at almost any time of the day, free of cost (Wikipedia defines Social Search as: “A type of web search method that determines the relevance of search results by considering the interactions or contributions of users”).

The ideal world does not exist for now (Kaliyug you see? ;-)). Though all experts might not be ready to offer their services to us selflessly, there always exist a number of such good patrons. Wikipedia wouldn’t have existed without such guys. Also a small amount of social incentive (something like adding 5 stars below the author’s name :D) can turn other not-so-selfless experts into contributors.

Now think, wouldn’t it be a lot better to get instant answers to your questions from experts, always happy to chat with you through an Instant Messaging Service like Goggle Talk? Interactions through chats would be a lot more fruitful than those online Q-A forums where you post a question and wait for someone to wake up and answer it.  This is exactly what a group of friends thought and formed a start-up in San Francisco, The Mechanical Zoo.  And then what we got was…

Aardvark

If people are the prime source of information why not tap the source directly? Aardvark was established with exactly this aim.

Everyone might not be an expert. But you are as good as one to me if you know something that I don’t and which I want to know (it could be as simple as knowing the location of a Salsa Dance Class or a Coffee Shop in an area).  Even if you do not know the answer yourself, it would be good enough for me if you could possibly point/direct me to the right source of information on the internet OR to an expert that you know who could possibly know the answer or the correct source to the answer OR another expert that he knows who could possibly know…  See the recursion? ;) That’s how Aardvark works! It’s a way of getting answers to your questions from people who have them!

Interesting isn’t it?

“Aardvark was founded in late 2007 by Max Ventilla, Damon Horowitz, Nathan Stoll, and Rob Spiro. Aardvark was conceived as the first Social Search engine: a way to find people, not web pages, that have specific information.”

You can read about the research behind Aardvark and more here at their blog!  Here is a snapshot:

“Our research team is constantly making improvements to the AI system that figures out which Aardvark users are the best match to answer a question.  About halfway through this past year, our technology became ready for prime time: we passed the threshold of 90% questions answered, most in under 5 minutes!”

I am using Aardvark since a few months now and I am amazed to see what all it can do. Aardvark is continuously evolving and is getting equipped with new useful features. I can hardly wait to see how powerful Aardvark would become in a few years time from now with its committed development team and increasing user base…

Btw, other (BIG!) companies are also making their presence felt in the Social Search arena. Any wild guesses???

PS: I guess there is a little secret behind choosing the name Aardvark; other than the obvious one that it is the name of an animal (suits the company name, Mechanical Zoo!). Aardvark is the first word in the English Dictionary. So how does it matter? Oh! Come-on guys! Think what would happen when you add Aardvark to your gtalk or yahoo friend’s list? It would always appear on the top. Brilliant isn’t it? :-)

This is how every computer programming book starts… Frankly, I did not know how else to start my first blog, so this!

Though, this blog is not really about programming. It is about, umm… let me think… I don’t know… I leave it for you to figure it out.

So, what is it about starting the blog so late? (I was thinking of blogging since a few years!) There is always this mental inertia in human minds against starting something new; even though it would be something that they want to or would love to do. Like my plans of joining a gym. But that’s a different story all together…

I had a thousand reasons to not start writing. The latest reason being washing clothes, including my under wears; which I would have none to wear to office tomorrow, if I don’t do the weekly washing now! But, today is THE day… No one can stop me from starting today… I can already feel the blood rushing inside me…

Let me think of a few good reasons for me to start writing this blog:

Writing a blog has been there in my todo-list for a long time… I want to remove it from there to redeem some of my lost self esteem ;)

Secondly, I have already written a few things, and have invested some time in it. So it would be nice to have a place to dump all those (crap!) writings somewhere on the web so that it stops cluttering my drive. Also my hard disk might crash anytime! Or, worse my laptop may get stolen!!

Third one is a random reason which has just popped up in my mind… This would be a nice place to store all those trillion usernames and passwords (of course in encrypted form) which one has to remember throughout his/her life. All thanks to web 2.0 revolution or whatever they call it. I would finally have some freed space in my brain which could be used for something worth remembering rather than this username-password shi*!

Finally, Joel thinks writing is one of the 9 cool things that a budding programmer should do. I think it’s never too late to follow his advice!

That’s all for now… Welcome aboard :)

PS: I offer my prayers to the Web 2.0 goddess (I hope there is one by now) to keep me as much motivated as possible, so that I could write regularly on this blog. Amen!

PS:PS: What a co-incidence! The default blog-post title @wordpress is “Hello world!”  smiles!!