Sudoku

Last January we visited the Burmeisters in California. I noticed that Fred was fully engaged working puzzles in the newspaper and wondered what that was all about. So I tried one of the Sudoku puzzles and was instantly hooked. Unlike crossword puzzles, it required nearly zero knowledge, just the abiliity to think logically. On the surface, the puzzle concept is simple and like any other puzzle, some are easy and some are hard so as you gain experience you drift up in complexity. And that’s been my experience so when we buy puzzle books, I move right to the ones labeled tough or demanding or challenging, or tricky, or diabolical – any of the adjectives that indicate a tough puzzle. I leave the easy and moderates to Nancy who is not nearly as engaged in solving these puzzles as I am.

But here’s where I have some difficulty. I also do the ones in the newspaper every day. These are graded one to four with one being the easiest. So throughout the week I do a few ones, a few two’s etc. What I find is that sometimes I breeze through a “four” and other times I get stuck on a “one”. It makes me wonder how they rate the complexity.

The most obvious thought would be that a simple puzzle has more filled in starting numbers and a more complex puzzle would have fewer. But I don’t think that has anything to do with it. Some of those rated most difficult have 20-22 blocks filled in (out of 81 possible); some of those labeled simple have 22 – 24. But if you think about it, if it were true that the more numbers you have filled in the easier the puzzle, then with each number you add the puzzle would get easier. For example if you started with 20 given locations and added another 10, why is that any different that starting out with one that has 30 numbers filled in and even the ones labeled super easy have fewer than 30 filled in to start with. So it stands to reason that once you had 30 filled in, the rest should be child’s play. Wrong!

Another something I noticed is that after getting totally stuck on a puzzle, if I erase it and start over using a different starting point, the puzzle sometimes melts away with ease. For example I usually attack the square in the upper left corner and then move left to right, top to bottom, exactly as if reading a book. After going through all 9 blocks that way, I systematically attack it on a column by column basis, again left to right; then on a row by row basis, top to bottom. I will deviate from this circular approach to pick up gimme’s but nominally I continue the rotation until it comes up blank. I have another technique that I use beyond that but I won’t get into that detail. But when I start say from the lower right hand corner block and work backwards, then do rows before columns etc – I don’t hit a stop at the same point. I may get way further one way and even solve one that had me tearing out my hair. Meaning that the sequence with which I attacked the puzzle rendered it either difficult or easy. That just defies logic – or at least my logic – but I’ve tried that on several puzzles and it seems to bear out. It doesn’t mean that I solve one that had me stumped but it does often enough to assure me that there’s something to the sequencing. And even when I don’t solve it the second time, my total count when I hit a stop point is different than it was originally. Telling me that sequencing surely has something to do with it.

So how do the creators of these puzzles decide which ones are easy and which are not quite so easy and which are brutal? Inquiring minds want to know.

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