FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in          Games  Calendar Log in to check your private messages    Some nice, very hard, Sudoku's Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8          Sudoku Programmers Forum Index -> Solving sudoku View previous topic :: View next topic   Author Message Kiudee Joined: 01 May 2006 Posts: 4 : Items Posted: Sat May 06, 2006 5:02 pm    Post subject: Now this one here is really hard (rates 41003 in Into Sudoku - 3x guessing): Code: 6..9.5..79.......8.7..8..3...73.68.............317.5...9..5..2.2.......17..6..... Code: 6 . .|9 . 5|. . 7 9 . .|. . .|. . 8 . 7 .|. 8 .|. 3 . -----+-----+----- . . 7|3 . 6|8 . . . . .|. . .|. . . . . 3|1 7 .|5 . . -----+-----+----- . 9 .|. 5 .|. 2 . 2 . .|. . .|. . 1 7 . .|6 . .|. . . Let me see what your solvers report while solving this 'monster' Back to top Carcul Joined: 29 Dec 2005 Posts: 50 : Location: Coimbra, Portugal Items Posted: Wed May 17, 2006 6:24 pm    Post subject: Kiudee wrote: Now this one here is really hard (...) Let me see what your solvers report while solving this 'monster' Here's what my "solver" has to say about your puzzle: Code:  *----------------------------------------------------------*  | 6    1348  1248 | 9    134    5     | 124    14     7    |  | 9    134   124  | 247  6      1347  | 124    5      8    |  | 145  7     1245 | 24   8      14    | 69     3      69   |  |-----------------+-------------------+--------------------|  | 145  1245  7    | 3    249    6     | 8      149    249  |  | 148  1246  9    | 5    24     248   | 1467   1467   3    |  | 48   246   3    | 1    7      2489  | 5      469    2469 |  |-----------------+-------------------+--------------------|  | 3    9     1468 | 478  5      147   | 467    2      46   |  | 2    458   4568 | 478  349    3479  | 34679  46789  1    |  | 7    148   148  | 6    12349  12349 | 349    489    5    |  *----------------------------------------------------------* 1. [r1c8](-1-[r12c7]=1=[r5c7]-1-[r5c1])-1-[r1c5]=1=[r9c5](-1-[r9c23]=1|9=[r9c8]-9-[r4c8])=2=[r9c6]-2-[r5c16]-4-[r5c5]=4=[r4c5]-4-[r4c8]-1-[r1c8], => r1c8 cannot be "1". 2. [r7c4]=8=[r7c3]-8-[r1c3]=8=[r1c2]=3=[r1c5]=1=[r9c5]-1-[r7c679]-4,7-[r7c4], => r7c4 cannot be "4,7". 3. [r8c8]=8=[r9c8]=9|1=[r9c23]-1-[r7c3]=1=[r7c6]=7=[r7c7]-7-[r8c8], => r8c8 cannot be "7". 4. [r5c7]=4=[r46c9]-4-[r7c9]-6-[r3c9]=6=[r3c7]-6-[r5c7], => r5c7 cannot be "6". 5. [r2c4]=7=[r8c4]-7-[r7c6]-1-[r3c6]-4-[r2c4], => r2c4 cannot be "4" and the puzzle is solved. Carcul Back to top Henk Joined: 13 Nov 2005 Posts: 105 : Items Posted: Thu Nov 09, 2006 9:28 pm    Post subject: I improved the solver and generator in Into Sudoku. It now can solve more puzzles, but whats more importand it can find all backdoors in a puzzle! A backdoor is a candidate which breaks down a hard puzzle into a very simple puzzle. Allmost every puzzle has more then one backdoor. After finding a backdoor, Into Sudoku can try to solve any of those backdoors. Right now, its not that efficient as for example Carcul, but its a start. The next step will be finding he optimal solving path. This puzzle has no backdoors, and thus cannot be solved in one advanced step according to Into Sudoku: Code:  . . . | . . . | 1 4 .  . . 1 | . . 8 | 5 . 9  . 2 . | . 9 . | . 6 . -------+-------+------  1 . . | 4 . . | . 2 .  . . 8 | . 6 . | . . 4  . . . | . . 7 | 9 . . -------+-------+------  . . 4 | 3 . 6 | . . .  8 3 . | . . . | . 9 .  . . . | . . . | 2 . .  35679  56789  35679  | 2567   2357   235    | 1      4      2378   3467   467    1      | 267    2347   8      | 5      37     9       3457   2      357    | 157    9      1345   | 378    6      378    ----------------------+----------------------+----------------------  1      5679   35679  | 4      358    359    | 3678   2      35678  23579  579    8      | 1259   6      12359  | 37     1357   4       23456  456    2356   | 1258   12358  7      | 9      1358   13568 ----------------------+----------------------+----------------------  2579   1579   4      | 3      12578  6      | 78     1578   1578   8      3      2567   | 1257   12457  1245   | 467    9      1567   5679   15679  5679   | 15789  14578  1459   | 2      13578  135678 _________________ Generate and solve Sudoku puzzles with Into Sudoku! Back to top daj95376 Joined: 05 Feb 2006 Posts: 349 : Items Posted: Thu Nov 09, 2006 10:48 pm    Post subject: Henk, You may wish to review the effect of the following assignments on the PM you posted. Code: r7c1    =  7     backdoor single r5c1    =  3     backdoor single r6c9    =  3     backdoor single r9c9    =  7     backdoor single Back to top Henk Joined: 13 Nov 2005 Posts: 105 : Items Posted: Fri Nov 10, 2006 7:48 am    Post subject: daj95376: The program does only check for backdoors that only need 1 candidate to be removed. It might be nice to also expand this by searching for cells that are a backdoor when it is solved. Maybe this puzzle can be solved with a single advanced step after all.... _________________ Generate and solve Sudoku puzzles with Into Sudoku! 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