The New Sudoku Players' Forum

[QBasicMac]

the one i posted retains the symmetry and thus has some chance of being the original puzzle before it got mangled.

Yep, good strategy: Drop clues in pairs. The final puzzle you posted has 11 pairs which could be dropped one at a time to see if the puzzle is still valid.

a) Not interested in doing that

b) Not interested in working on the resulting boring-hard puzzles.



Mac

[Pat]

there's 8 minimal 22s and 1 23

when dropping redundant clues,
there's the important question of the difficulty-level of the resulting puzzle!


so, i've now loaded them all into a sudbook -

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<sudoku-book>
<user>0</user>
<last>000000000000</last>
<checked>000000000000</checked>
<xtra>0</xtra>
<puzzle-type>0</puzzle-type>
<cells-in-row>9</cells-in-row>
<boxes-across>3</boxes-across>
<boxes-down>3</boxes-down>
<featuredGrade>Medium</featuredGrade>
<puzzle> <serial>1</serial> <grade>Medium</grade> <solvers>0000</solvers> <question> ...5......9..68.7...1...3...7..2...6.5.....8.8...4..9...9...1...8.67..3......2... </question> </puzzle>
<puzzle> <serial>2</serial> <grade>Medium</grade> <solvers>0000</solvers> <question> ...5......9..68.7...1...3...7..2...6.5.....8.8...46.....9...1...8.67..3......2... </question> </puzzle>
<puzzle> <serial>3</serial> <grade>Medium</grade> <solvers>0000</solvers> <question> ...5......9..68.7...1...3...7..2...6.5.....8.8...46.9...9...1...8.67.........2... </question> </puzzle>
<puzzle> <serial>4</serial> <grade>Medium</grade> <solvers>0000</solvers> <question> ..85......9..68.7...1...3...7..2...6.5.....8.....4..9...9...1.....67..3......28.. </question> </puzzle>
<puzzle> <serial>5</serial> <grade>Medium</grade> <solvers>0000</solvers> <question> ..85......9..68.7...1...3...7..2...6.5.....8.....4..9...9...1...8.67..3......2... </question> </puzzle>
<puzzle> <serial>6</serial> <grade>Medium</grade> <solvers>0000</solvers> <question> ..85......9..68.7...1...3...7..2...6.5.....8.....46.....9...1...8.67..3......2... </question> </puzzle>
<puzzle> <serial>7</serial> <grade>Medium</grade> <solvers>0000</solvers> <question> ..85......9..68.7...1...3...7..2...6.5.....8.....46.9...9...1.....67.........28.. </question> </puzzle>
<puzzle> <serial>8</serial> <grade>Medium</grade> <solvers>0000</solvers> <question> ..85......9..68.7...1...3...7..2...6.5.....8.....46.9...9...1...8.67.........2... </question> </puzzle>
<puzzle> <serial>9</serial> <grade>Medium</grade> <solvers>0000</solvers> <question> ..85......9..68.7...1...3...7..2...6.5.....8.8...46.....9...1.....67..3......28.. </question> </puzzle>
</sudoku-book>

just to check up on the difficulty-level,
and here are the results:

...5......9..68.7...1...3...7..2...6.5.....8.8...4..9...9...1...8.67..3......2... Very Hard
...5......9..68.7...1...3...7..2...6.5.....8.8...46.....9...1...8.67..3......2... Very Hard
...5......9..68.7...1...3...7..2...6.5.....8.8...46.9...9...1...8.67.........2... Medium

..85......9..68.7...1...3...7..2...6.5.....8.....4..9...9...1.....67..3......28.. "not valid"
..85......9..68.7...1...3...7..2...6.5.....8.....4..9...9...1...8.67..3......2... Unfair
..85......9..68.7...1...3...7..2...6.5.....8.....46.....9...1...8.67..3......2... "not valid"

..85......9..68.7...1...3...7..2...6.5.....8.....46.9...9...1.....67.........28.. Medium
..85......9..68.7...1...3...7..2...6.5.....8.....46.9...9...1...8.67.........2... Medium
..85......9..68.7...1...3...7..2...6.5.....8.8...46.....9...1.....67..3......28.. Very Hard


~ Pat

[Ruud]

Hi Pat,

surprised about these results, I used SudoCue to check these puzzles:

Code: Select all

...5......9..68.7...1...3...7..2...6.5.....8.8...4..9...9...1...8.67..3......2... 2 XW, 1 NT, 1 HP
...5......9..68.7...1...3...7..2...6.5.....8.8...46.....9...1...8.67..3......2... 1 XW, 1 NP
...5......9..68.7...1...3...7..2...6.5.....8.8...46.9...9...1...8.67.........2... -
..85......9..68.7...1...3...7..2...6.5.....8.....4..9...9...1.....67..3......28.. 2 TB
..85......9..68.7...1...3...7..2...6.5.....8.....4..9...9...1...8.67..3......2... 1 FF, 1 XY, 2 XW, 1 HP, 1 NP, 1 NT
..85......9..68.7...1...3...7..2...6.5.....8.....46.....9...1...8.67..3......2... 7 TB
..85......9..68.7...1...3...7..2...6.5.....8.....46.9...9...1.....67.........28.. -
..85......9..68.7...1...3...7..2...6.5.....8.....46.9...9...1...8.67.........2... -
..85......9..68.7...1...3...7..2...6.5.....8.8...46.....9...1.....67..3......28.. 1 XW, 1 NP

NP=naked pair, NT=naked triple, HP = hidden pair, HT=hidden triple,
XW=X-wing, XY=XY-wing, FF=Finned fish/colouring, TB=Tabling

There are no invalid sudokus here. Just 2 very hard, requiring tabling (bifurcation or guessing).
There is 1 that I would rate "Nightmarisch" for the blend of techniques, but it starts with 14 singles, which is not good enough for a Nightmare.
3 of them require nothing but singles. They would go into the "Easy" category. Narrowness of the solving path is constantly 3 or more. (3 alternatives available at any given time)

cheers,
Ruud.

[Pat]

surprised about these results---

There are no invalid sudokus here. Just 2 very hard, requiring tabling (bifurcation or guessing).

3 of them require nothing but singles. They would go into the "Easy" category.

thanks, Ruud!

no surprise - these are the Pappocom ratings.
( i took a minute with Excel to transform them into the sudbook shown. )

the 3 easiest puzzles are Pappocom-rated as Medium.

the 3 toughest puzzles are Pappocom-rated as either Unfair or "not valid"
- which merely means they're tougher than anything which Pappocom would generate.
( does not mean the puzzle is invalid! )


by the way, Ruud, in the first puzzle — the one which i solved — with 2 X-wings — i found the trio unnecessary, used a second duo instead.


spirit_fantasy, are you still there?
do you want help with this puzzle?

Code: Select all

 . . . | 5 . . | . . .
 . 9 . | . 6 8 | . 7 .
 . . 1 | . . . | 3 . .
-------+-------+------
 . 7 . | . 2 . | . . 6
 . 5 . | . . . | . 8 .
 8 . . | . 4 . | . 9 .
-------+-------+------
 . . 9 | . . . | 1 . .
 . 8 . | 6 7 . | . 3 .
 . . . | . . 2 | . . .

~ Pat

[coloin]

Spirit F's original grid -

Code: Select all

+---+---+---+
|..8|5..|...|
|.9.|.68|.7.|
|..1|...|...|
+---+---+---+
|.7.|82.|..6|
|.5.|...|.8.|
|8..|.4.|.9.|
+---+---+---+
|..9|...|1..|
|.8.|67.|.3.|
|...|..2|...|
+---+---+---+

Is made a valid puzzle by adding only ONE clue - the 3 in r3c7

Code: Select all

+---+---+---+
|..8|5..|...|
|.9.|.68|.7.|
|..1|...|3..|
+---+---+---+
|.7.|82.|..6|
|.5.|...|.8.|
|8..|.4.|.9.|
+---+---+---+
|..9|...|1..|
|.8.|67.|.3.|
|...|..2|...|
+---+---+---+ two clues are superfluous and can be removed as above

- tell us how you did it!

http://magictour.free.fr/suexmult.exe

txt file :
mask - [2=given clue,1=possible clue] [0=omitted]]
solution grid[s]

essentially it goes through all the ways to add a specified number of clues over a given grid[s]

Code: Select all

112211111121122121112111111121221112121111121211121121112111211121221121111112111
238517649594268371761394825973825416456931782812746593629483157185679234347152968
238517649594268371761493825973825416456931782812746593629384157185679234347152968
238517649594268371761934825973825416456391782812746593629483157185679234347152968
248517369395268471761394825473829516952136784816745293629483157584671932137952648 - here are four of the other 198 solution grids
....................................................................................
728513649395468271641297358973825416456139782812746593569384127284671935137952864 - the solution grid

Run from C:\
suexmult <file.txt> 1 1 will give the solution for one added clue[s]
suexmult <file.txt> 2 1 will mult two clues and so on

Output

Code: Select all

C:\suxx>suexmult 199.txt 1 1
..85......9..68.7...1...3...7.82...6.5.....8.8...4..9...9...1...8.67..3......2...

- i don't have any software to help me find the redundant clues.

Which can be reduced to a 22 clue minimal puzzles in only two ways
Using http://magictour.free.fr/suex9s.exe

Code: Select all

..85......9..68.7...1...3...7..2...6.5.....8.....4..9...9...1...8.67..3......2...
...5......9..68.7...1...3...7..2...6.5.....8.8...4..9...9...1...8.67..3......2... - your post

And http://magictour.free.fr/suexmu35.exe this will print only minimal puzzles.

Regards to all

[Pat]

MagicTour.Free.Fr/sudoku.htm

• suexmult
  
• suex9s
• suexmu35

thanks, coloin,
an important resource!