The upper-left box in the Pappocom sudoku
published in the Buffalo News (and, presumably,
many other newspapers) today, the Sunday
after Pi Day, contains the three digits 314.
Mere coincidence, or Intelligent Design?
Here it is:
300.000.604
010.002.000
004.701.200
000.800.705
000.000.000
407.005.000
003.607.100
000.900.080
106.000.002
One thing I have not seen is sudoku puzzles that start
with an obvious shape of filled-in cells, such as a
block-letter E, Z, a Star of David, or a swastika.
Most such problems will have to be overconstrained,
i.e., containing more filled-in cells than are necessary
for a unique solution. A set of five such sudoku
could spell out HELLO. But soft! A sudoku filled
in in an L pattern would have 9+9-1 = 17 filled-in
cells, which I think is the lower limit for a sudoku
to have a unique solution.
So there's a challenge for sudoku constructors:
Come up with a sudoku puzzle whose given cells
are the leftmost column and the bottommost row,
to form an L pattern.
(Or a proof that such a sudoku is impossible.)
-- Mark Spahn (West Seneca, NY)
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