Nearly all my life, I have mentally labeled puzzles as time-wasting. I have heard of the idea that crosswords and sudoku and acrostics and such are good for the brain but I didn’t care. Mostly, I still don’t. On a cruise a few years ago, Lynn and I started doing the ship’s daily sudoku together. She is a big puzzle fan and can do four at a time, a pencil in each hand and held between the toes of each foot. Since she is obviously very sharp and had consistently good judgment, I figured it was time to learn a bit of how to do the 9x9 number puzzles.
For about a year, I have done one a day. Once in a while, two in a day. My friend told me that she likes sudoku but considers crossword puzzles to be better for her. Her interesting criterion is that after doing a sudoku, she can’t remember it but she can remember words and definitions and clues from a crossword puzzle.
I learned that one way to start a sudoku is look at the 3x3 in the upper left. Select the first figure that is given and check whether that same figure appears in either of the 3x3’s below. If it appears in all three 3x3’s, go to the next figure. If it appears in two of the 3x3’s but not the third, you may be able to see which is the only cell for that figure.
Using that approach, checking for two of three occurrences in vertical sets and then in horizontal sets is a good start. Checking each 3x3 for patterns that will allow verified placement of a missing figure is a good next step. For a long while, two of three and each 3x3 separately were my main steps. Over the last couple of months, making use of the fact that each 9-cell column and 9–cell row must contain exactly one of each digit has overtaken the other methods for speed and power.
Yesterday, I worked on an easy sudoku for a 2nd hour. I had stared at the dumb thing for an hour the previous day. But the end of the 2nd hour, I asked my resident puzzler for help. I have consistently done only officially labeled “easy” sudokus on the grounds that the diabolical ones aren’t fun but torture. When Lynn does them, she needs her special automatic pencil and her large eraser at the ready. She must use little erase-able notes in difficult cells. Once the notes reveal that say, a given cell can only contain a certain figure, all other such notes must be erased and the figure is place in that only possible cell.
I have ordered a breathing mask, an automatic pencil and a large eraser. I may descend into the wilderness of eraser dust and try those little notes. In five minutes, my advanced partner showed me how the notes broke the logjam and made clear what goes where, five minutes after two fruitless hours.
