Solution to Ocean's #6/gold

Advanced methods and approaches for solving Sudoku puzzles

Solution to Ocean's #6/gold

Postby gurth » Mon Nov 20, 2006 9:35 am

Solution to Ocean's #6/gold
Code: Select all
 *-----------*
 |..1|..2|...|
 |.3.|.4.|.5.|
 |6..|7..|8..|
 |---+---+---|
 |..8|...|..7|
 |.1.|...|.4.|
 |9..|...|5..|
 |---+---+---|
 |..4|..1|..8|
 |.2.|.3.|.1.|
 |...|6..|9..|
 *-----------*    gsfr=99909 ER=N/A


Note: This solution is designed to be followed using the Simple Sudoku program.
"..." means proceed as far as SS allows, following the hints given by SS in the order given.
This will facilitate rapid checking of this solution.

"?" introduces a move that will be disproved by contradiction. (These moves are only introduced when SS grinds to a halt, saying "no hint available".) In order to "play" this move, you will have to turn off the "block invalid moves" feature of the program. Then insert the move and follow all hints given until you see a contradiction. Once you find the contradiction, you must retrace (withdraw in reverse order) all moves made since the disproved move, by clicking the "undo" arrow repeatedly. Then "correct" the disproved move. EG if this move was "?3f6", then REMOVE the 3 at f6, because you have proved the 3 at f6 false.

Solution:

(1) 8f8, 1k1...

(2) ?4a2... (?6h3...??)-6h3...?? -4a2, -4d6(MC).

(3) ?4c9... (?1d4...??)-1d4... (?6h3... ((?9c6...??))-9c6...??)-6h3...?? -4c9...

(4) ?4h4... (?1f9... ((?6h7...??))-6h7...??)-1f9... (?3c8...??)-3c8, (?3a4......??)-3a4... (?3a8...??)-3a8... (?3d8...??)-3d8...?? -4h4....

(5) ?1b7... (?6f2... ((?7f6...??))-7f6...??)-6f2... (?8b1...??)-8b1... (?6f3...??)-6f3... (?5a2...??)-5a2, (?8a1...??)-8a1...?? -1b7....

(6) ?2g8...?? -2g8.

(7) ?2k8...?? -2k8...(MC).

(8) ?2e9...?? -2e9.

(9) ?2e7...?? -2e7.... End.
_______________________________

Note judicious use of 3 sub-sub-nets. The time to use them is when the argument is far advanced, few candidates remain on the board, and a sub-sub-net is sure to be short and easy.
_______________________________
gurth
 
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Joined: 11 February 2006
Location: Cape Town, South Africa

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