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| chuckfresno
| Joined: 16 Jun 2005 | Posts: 39 | : | | Items |
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Posted: Mon Aug 08, 2005 2:24 pm Post subject: "Probably Too Hard" by Hirofumi Fujiwara |
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Code: |
. . 2 | . 5 . | . 8 .
. 7 . | . . . | 4 . .
4 . . | 9 . 2 | . . .
-------+-------+------
. . 4 | . 8 . | . . 1
. 6 . | . . . | . 4 .
1 . . | . 6 . | 5 . .
-------+-------+------
. . . | 5 . 9 | . . 6
. . 5 | . . . | . 7 .
. 8 . | . 2 . | 3 . .
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This one was composed by Hirofumi Fujiwara, a long time puzzle composer and programmer for Nikoli. The puzzles that are normally published are never hard by the standards set here. He called this one "Probably Too Hard" and placed it here. |
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| dukuso
| Joined: 14 Jul 2005 | Posts: 424 | : | Location: germany | Items |
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Posted: Mon Aug 08, 2005 6:03 pm Post subject: |
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takes my solver 0.5ms
normal is less than 0.2ms
my 50 hardest ones take 0.9ms in average
currently hardest with 2.8ms is this one:
....1.78.5....9..........4..26.........6....3.74.8.........3..2.8..4..1.6..5..... |
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| nj3h
| Joined: 29 Jul 2005 | Posts: 9 | : | Location: Virginia - USA | Items |
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Posted: Mon Aug 08, 2005 8:59 pm Post subject: |
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Unless I typed it in wrong, Pappocom indicates it is not a valid puzzle. Simes' solver will not solve it. As Simes' website indicates, he has not implemented some of the techniques as of yet, so I suspect that must be the reason there. |
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| angusj Site Admin
| Joined: 18 Jun 2005 | Posts: 406 | : | | Items |
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Posted: Mon Aug 08, 2005 10:56 pm Post subject: |
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nj3h wrote: | Unless I typed it in wrong, Pappocom indicates it is not a valid puzzle. |
It has a single solution, so in that (the most important) sense it's valid. |
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| kranser
| Joined: 18 Aug 2005 | Posts: 35 | : | | Items |
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Posted: Thu Aug 18, 2005 2:05 pm Post subject: |
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angusj wrote: | nj3h wrote: | Unless I typed it in wrong, Pappocom indicates it is not a valid puzzle. |
It has a single solution, so in that (the most important) sense it's valid. |
I thought that a valid 9X9 puzzle had to have at least 23 starting values. I haven't read this whole forum yet, so please forgive me if this topic has been covered already.
What patterns does this puzzle require to solve?
Kranser. |
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| Merri
| Joined: 02 Aug 2005 | Posts: 44 | : | | Items |
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Posted: Thu Aug 18, 2005 3:46 pm Post subject: |
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A valid 9 x 9 puzzle can have as few as 17 starting values and still have only one solution. You can find these on this forum by searching for "minimal sudoku". |
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| kranser
| Joined: 18 Aug 2005 | Posts: 35 | : | | Items |
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Posted: Thu Aug 18, 2005 4:26 pm Post subject: |
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Merri wrote: | A valid 9 x 9 puzzle can have as few as 17 starting values and still have only one solution. You can find these on this forum by searching for "minimal sudoku". |
Thanks Merri for your reply. Do minimal sudoku's require guess to be made when they are solved, or can they be solved purely by logic patterns? |
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| Merri
| Joined: 02 Aug 2005 | Posts: 44 | : | | Items |
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Posted: Thu Aug 18, 2005 8:16 pm Post subject: |
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You'll have to ask that from the people who create logics that require no guessing. Probably there is always a logic to solve a sudoku. Since I haven't such a logic in my hands, I can't really give a definite answer. However there are some 17 clues puzzles that can be solved with the most basic logics. |
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| chuckfresno
| Joined: 16 Jun 2005 | Posts: 39 | : | | Items |
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Posted: Sat Aug 20, 2005 2:30 am Post subject: |
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kranser wrote: | Merri wrote: | A valid 9 x 9 puzzle can have as few as 17 starting values and still have only one solution. You can find these on this forum by searching for "minimal sudoku". |
Thanks Merri for your reply. Do minimal sudoku's require guess to be made when they are solved, or can they be solved purely by logic patterns? |
My personal experience is that 17-clue Sudokus are usually on the easy side, for example this one chosen at random requires only the simplest of beginner logic.
The more general question of whether any particular Sudoku can be solved "purely by logic patterns" depends completely on what methods you include. |
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