More changes at my sudoku site of choice:

First, they’ve added a new tool to help you solve puzzles: they’ll highlight all squares where you’ve filled in a given number (either as the only choice for that square or as one of the possibilities for that square). Which I appreciate: for one thing, it helps the algorithm that I use when starting to solve a new puzzle, and for another thing, it eliminates some of the mindless searching in the middle of solving a puzzle, where you just haven’t noticed that a square that used to be 134 is now just 14 because you’ve since filled in a 3 in the same row.

They’re doing a very good job of allowing me to eliminating the parts of filling out sudoku that I don’t enjoy (making stupid mistakes like two 4’s in the same row, mindless searches for numerical conflicts) while still leaving me enough to do that I have to spend some time thinking. I also find that I enjoy being the person who actually fills in the number that must go in a square: they have another optional feature “auto pencil marks” which fills in the possibilities for each square using a naive algorithm (eliminating all numbers that would conflict with the given row/column/block); I don’t use that, because I assume it would find a unique solution for several of the squares, and I want to find those unique solutions myself! So I’m willing to trade some amount of tedium for that feeling of accomplishment.

After my first sudoku post, Chris commented that he didn’t do them because he didn’t like puzzles that he could write a Perl script to solve. Which is a quite reasonable point of view, but it turns out that what I like is puzzles where I could write a Perl script to do a fair amount of the automation while leaving me with most of the thinking.

The second recent change is that they’ve gone from three to four to five difficulty levels. Honestly, I didn’t notice a big difference when they went to four (a little difference, but not a big one), but today is the first day with five difficulty levels, and, for the first time, my standard algorithms didn’t let me solve the puzzle. (Or at least the first time recently: previous puzzles have forced me to add to my bag of tricks.) So I had to figure out a new algorithm to get past that one; fortunately, the new algorithm was made easier to carry out by the “highlight all squares with a given number” feature.

The upshot is that I can still do their hardest sudoku more quickly than I could have done it when their hardest was significantly easier but I didn’t have as much automated help, and that I enjoy it more because I’m spending less time doing tedious searching and more time thinking. And it’s less of a time sink. A win all around.

(Enough with the sudoku posts, I know.)

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