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An 8x8 subtractions only (a little bit more difficult)
http://www.calcudoku.org/forum/viewtopic.php?f=16&t=127
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Author:  clm  [ Mon Dec 05, 2011 12:09 pm ]
Post subject:  An 8x8 subtractions only (a little bit more difficult)

An 8x8 subtractions only (a little bit more difficult)

In my opinion the subtractions only puzzle (actually 7x7) is the “jewel of the crown” of the Calcudokus: elegant, clean, apparently simple and suddenly full of logic and sometimes difficulty. I have developped this new 8x8 subtractions only. I solved it, in the usual way, and found that it apparently has a unique solution. However I would like to confirm that unicity (we would not show the solution for a few days so that any interested calcudoker may try it) as well as the difficulty level (the “solver rating” in order to “compare it” with the normal 7x7 subtractions only) so, once more, Patrick, if you are so kind, here is the code:

8
1,-,a1b1
2,+,c1
1,-,d1e1
3,-,f1g1
1,-,h1h2
1,-,a2b2
4,-,c2c3
1,-,d2e2
4,-,f2f3
4,-,g2g3
1,-,a3b3
7,-,d3e3
2,-,h3h4
3,-,a4a5
2,-,b4c4
1,-,d4e4
3,-,f4f5
5,-,g4g5
2,-,b5c5
1,-,d5e5
4,-,h5h6
1,-,a6b6
5,-,c6d6
3,-,e6f6
6,-,g6g7
5,-,a7a8
3,-,b7b8
5,-,c7d7
3,-,e7f7
3,-,h7h8
3,-,c8d8
5,-,e8f8
5,+,g8

Image

Author:  pnm  [ Mon Dec 05, 2011 2:26 pm ]
Post subject:  Re: An 8x8 subtractions only (a little bit more difficult)

Yes, one solution, determined in 2.8 seconds.

Difficulty factor estimated at 149 (!)

Author:  sneaklyfox  [ Mon Dec 05, 2011 6:26 pm ]
Post subject:  Re: An 8x8 subtractions only (a little bit more difficult)

Nice puzzle and fun. Not significantly harder than 7x7 subtractions only but it is harder because of more possibilities.

Author:  clm  [ Tue Dec 06, 2011 12:37 am ]
Post subject:  Re: An 8x8 subtractions only (a little bit more difficult)

pnm wrote:
Yes, one solution, determined in 2.8 seconds.

Difficulty factor estimated at 149 (!)


Thank you, yes, that "solver rating" of 149 is significatively higher than the 66.9 assigned by the "solver rating" to the last 7x7 subtractions only, the wednesday's Nov 30, 2011 (Puzzle id: 378730). Will see the day after tomorrow.

The solution process requires the same strategies as for the 7x7's of that type but the number od possibilities increase (as sneaklyfox underlines) so that would explain the high difficulty factor (apparently higher than the 9x9's and among the 12x12's). Let's compare it with some very recent "difficult" puzzles, for reference:

Tuesday Nov 29, 9x9 (Puzzle id: 381109) (theorically the most difficult 9x9 during the week): factor 109.3

Thursday Dic 01, 12x12 (Puzzle id: 396281): factor 142.8

Sunday Dic 04, 12x12 (Puzzle id: 396314): factor 161.2

Author:  sneaklyfox  [ Tue Dec 06, 2011 2:34 am ]
Post subject:  Re: An 8x8 subtractions only (a little bit more difficult)

clm wrote:
pnm wrote:
Yes, one solution, determined in 2.8 seconds.

Difficulty factor estimated at 149 (!)


Thank you, yes, that "solver rating" of 149 is significatively higher than the 66.9 assigned by the "solver rating" to the last 7x7 subtractions only, the wednesday's Nov 30, 2011 (Puzzle id: 378730). Will see the day after tomorrow.

The solution process requires the same strategies as for the 7x7's of that type but the number od possibilities increase (as sneaklyfox underlines) so that would explain the high difficulty factor (apparently higher than the 9x9's and among the 12x12's). Let's compare it with some very recent "difficult" puzzles, for reference:

Tuesday Nov 29, 9x9 (Puzzle id: 381109) (theorically the most difficult 9x9 during the week): factor 109.3

Thursday Dic 01, 12x12 (Puzzle id: 396281): factor 142.8

Sunday Dic 04, 12x12 (Puzzle id: 396314): factor 161.2


I guess this goes back to the question of how the difficulty factor is calculated. Generally I find the patterned 9x9s, say ~110 harder than the 12x12s ~140.

Author:  pnm  [ Tue Dec 06, 2011 11:35 am ]
Post subject:  Re: An 8x8 subtractions only (a little bit more difficult)

sneaklyfox wrote:
I guess this goes back to the question of how the difficulty factor is calculated. Generally I find the patterned 9x9s, say ~110 harder than the 12x12s ~140.

There is a "division by size" in the formula, but I'm thinking that's not strong enough.

Patrick

Author:  clm  [ Mon Dec 19, 2011 1:13 am ]
Post subject:  Re: An 8x8 subtractions only (a little bit more difficult)

pnm wrote:
Yes, one solution, determined in 2.8 seconds.

Difficulty factor estimated at 149 (!)


The solution:

Image

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