First we have to agree on some notation.

Similarly, read the next assignment statement as " is adictionary where each square maps to the set of squaresformed by the union of the squares in the units of , but not itself".

5 4 1 7 |3 6 9 |8 2 5 B1 B2 B3| B4 B5 B6| B7 B8 B9 .

This implies that each squaremust have a different value from any of its peers.

6 3 2 |1 5 8 |9 4 7 C1 C2 C3| C4 C5 C6| C7 C8 C9 .

Myguess is that somewhere early in the search there is a sequence of squares (probablytwo) such that if we choose the exact wrong combination of values to fill the squares, it takes about 190 seconds to discover that thereis a contradiction.

8 2 5 |4 3 7 |1 6 9 E1 E2 E3| E4 E5 E6| E7 E8 E9 .

Theresults were starkly bimodal: in 27 out of 30 trials the puzzle tookless than 0.02 seconds, while each of the other 3 trials took just about190 seconds (about 10,000 times longer).

Here are the names of the squares, a typical puzzle,and the solution to the puzzle:

So agrid where is and is empty would be represented as .

I knew, in that moment, that I'd be doing one of those things for mycareer. (I thought it'd be nanotechnology, actually; I didn't getconverted over to AI and cognitive science and computer programminguntilI read ) I read this book, and Irealized it was possible to solve the problems of theworld,that was beyond the reach of intelligence, that mygenerationand maybe even my grandparents' generation was going to be immortal,andI decided that I was going to help make it happen, and that's what mylifewould be.

Here is the code to parse a grid into a dict:

is about, you guessed it,evolutionarypsychology - the origin of our-modern day emotions as the frozenstrategiesof survival and reproduction from the days of the hunter-gatherers.

We could implement this as , but we can do morethan just that.

Then along came a book called "Great Mambo Chicken". As Irecall,it was taken out as a library book and given to me, for the duration ofthe loan, by a grand-uncle. Undoubtedly attracted by the title,ofcourse. And inside this book was...

"That which can be destroyed by the truth should be."

So each of the following three grid stringsrepresent the same puzzle:

The price Amazon currently quotes is $165, but I bought mine for $90at our local Microcenter. Is it worth it? Definitely. If you have to choose either a college curriculum incognitivescience or reading MITECS cover to cover, pick MITECS.

All other characters are ignored (including spaces,newlines, dashes, and bars).

Five years later, I've never looked back.

The function will return the updated (including the updates from constraint propagation), butif there is a contradiction--if the assignment cannot be madeconsistently--then returns .

One might think that a 9 x 9 arraywould be the obvious data structure.

Therefore, will be a dict with squares as keys.

Cryonics! The colonization of space! Fun with highexplosives! Humanity's conquest of the Universe! Artificialintelligence! Genetic engineering! Nanotechnology! The Omega Point! Ultratechnologies by the dozen!