The Boston Globe just started running them daily last week. Definitely the hot puzzle this year; we'll see if it lasts. The Globe's puzzles got harder throughout the week: Monday my 6-year-old son could do, while Saturday's definitely required some more sophisticated solving strategies. Hmm, I don't have that one to hand, but here's last Friday's still sitting in my wastebasket; I don't recall how hard it was: - 5 3 | - 7 - | - 9 - 6 - - | - 1 2 | - - 8 - - - | - - - | - - 7 ------+-------+------ - 6 - | - 8 - | - - - 9 7 - | 4 - 1 | - 5 2 - - - | - 2 - | - 7 - ------+-------+------ 3 - - | - - - | - - - 7 - - | 8 6 - | - - 4 - 4 - | - 5 - | 1 3 - Or go to websudoku.com and try one of their puzzles rated "Hard" or "Evil". A central tenet of sudoku puzzles is that they should be solvable "by logic alone", which is to say, without any trial-and-error. This sparks religious battles within the sudoku-solving community, as people argue over whether certain techniques are legitimate logic or just glorified guess-and-check. Of course, what techniques you recognize as legitimate dictates how you rate the difficulty (or even the solvability) of various puzzles. --Michael Kleber On 7/18/05, Richard Schroeppel <rcs@cs.arizona.edu> wrote:
I was puzzled about Sudoku, mentioned in a recent message. It's apparently well known on the puzzle circuit. Here's an example I swiped from last Monday's USA Today -- they've started running a daily puzzle.
- 6 - | 3 - 8 | - 7 - - - - | - - - | - - - 4 3 - | 6 - 1 | - 9 5 ------+-------+------ - - 5 | - 4 - | 7 - - - - - | - 1 - | - - - - - 1 | - 2 - | 8 - - ------+-------+------ 9 2 - | 4 - 5 | - 3 6 - - - | - - - | - - - - 8 - | 7 - 9 | - 4 -
In a completed sudoku, each row and column of the puzzle has one occurence of each digit from 1-9. (This makes it a Latin Square.) In addition, each of the nine marked 3x3 subsquares has (one of) each digit. The solver's job is to fill in the blanks in the puzzle. I think the one above would qualify as simple; I was able to complete it without much "advanced reasoning".
Rich rcs@cs.arizona.edu
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