Sudoku Players' Forum (clone)

by **Fortesque92** » Sat Oct 14, 2023 4:13 am

by **Hajime** » Sat Oct 14, 2023 5:44 am

Original puzzle:

Code: Select all: 9...1.7..3..5.9..............6...4.9.5..7.8...8.4..2....73..6.1.....1.7.4...96.2

.

After basics

Code: Select all: +-----------+------------+-----------+ | 9 246 5 |268 1 248| 7 48 3 | | 3 7 28| 5 248 9 | 1 6 248| | 68 246 1 |268 3 7 |59 489 2458| +-----------+------------+-----------+ | 7 3 6 | 1 28 28| 4 5 9 | | 2 5 4 | 9 7 3 | 8 1 6 | | 1 8 9 | 4 6 5 | 2 3 7 | +-----------+------------+-----------+ | 58 29 7 | 3 2458 248| 6 489 1 | |568 269 238| 28 2458 1 |39 7 48 | | 4 1 38| 7 9 6 |35 2 58 | +------------------------------------+ 9.5.1.7.337.5.916...1.37...7361..459254973816189465237..73..6.1.....1.7.41.796.2.

One XYZ wing ( b7e2 means box 7 element/cell 2 )
XYZ-Wing Type B on {239} in b7e2,b7e6,r8e7 (-9)b7r8 => (-9)r8c2
stte

by **eleven** » Sat Oct 14, 2023 10:08 am

There is no such xyz-wing, because r8c3 is 238, not 239.

Without using chains, you probably need 5 steps like this:

Code: Select all: *---------------------------------------------------------------* | 9 246 5 | 268 1 248 | 7 48 3 | | 3 7 28 | 5 #248 9 | 1 6 #248 | | 68 246 1 | 268 3 7 | 59 489 258-4 | |--------------------+---------------------+--------------------| | 7 3 6 | 1 28 28 | 4 5 9 | | 2 5 4 | 9 7 3 | 8 1 6 | | 1 8 9 | 4 6 5 | 2 3 7 | |--------------------+---------------------+--------------------| | *58 29 7 | 3 *258-4 24-8 | 6 489 1 | | 568 269 238 | *28 #2458 1 | 39 7 #48 | | 4 1 38 | 7 9 6 | 35 2 58 | *---------------------------------------------------------------*

x-wing 4r28c49 (#) -> -4r7c5,r3c9
xyz-wing 258 r7c15,r8c4 (*) -> -8r7c6

Code: Select all: *---------------------------------------------------------------* | 9 246 5 | 268 1 248 | 7 48 3 | | 3 7 28 | 5 248 9 | 1 6 248 | | 68 246 1 | 268 3 7 | 59 489 258 | |--------------------+---------------------+--------------------| | 7 3 6 | 1 28 28 | 4 5 9 | | 2 5 4 | 9 7 3 | 8 1 6 | | 1 8 9 | 4 6 5 | 2 3 7 | |--------------------+---------------------+--------------------| | 58 29 7 | 3 258 *24 | 6 89-4 1 | | 568 269 238 | *28 258-4 1 | 39 7 *48 | | 4 1 38 | 7 9 6 | 35 2 58 | *---------------------------------------------------------------*

xy-wing 28,4 r8c49,r7c6 (*) -> -4r7c8,r8c5

Code: Select all: +--------------------+----------------+----------------+ | 9 246 5 | 268 1 28 | 7 48 3 | | 3 7 #28 | 5 4 9 | 1 6 #28 | | 68 246 1 | 268 3 7 | 59 489 25-8 | +--------------------+----------------+----------------+ | 7 3 6 | 1 28 28 | 4 5 9 | | 2 5 4 | 9 7 3 | 8 1 6 | | 1 8 9 | 4 6 5 | 2 3 7 | +--------------------+----------------+----------------+ | 58 *29 7 | 3 258 4 | 6 8-9 1 | | 568 26-9 *23-8 | 28 258 1 |*39 7 4 | | 4 1 #38 | 7 9 6 | 35 2 #58 | +--------------------+----------------+----------------+

x-wing 8r29c39 (#) -> -8r3c9,r7c3
xy-wing 23,9 r8c37,r7c2 -> -9r7c8,r9c2

by **Hajime** » Sat Oct 14, 2023 11:22 am

eleven wrote:There is no such xyz-wing, because r8c3 is 238, not 239.

You were right, of course. I was too hasty...
To eliminate the naste 8 in r8c3 needs more methods

by **Fortesque92** » Sat Oct 14, 2023 8:43 pm

Wow, this is a tough one. Thanks!

by **Hajime** » Sun Oct 15, 2023 5:30 am

Fortesque92 wrote:Wow, this is a tough one. Thanks!

If you are up to an AIC, you only need this

Code: Select all: AIC Type 2 [5 links] (2)(2=9)r7c2-9-r7c8=(9-3)r8c7=3=r8c3 => (-2)r8c3 stte

Again in cell r8c3...

Stuck on a puzzle