The New Sudoku Players' Forum

by **urhegyi** » Sat Apr 17, 2021 8:41 am

Is the puzzle I just created a computer exercise or can anyone find a human logical solvepath?

Code: Select all: .....6....3..2...7..24...5..7..1....5......4...6.3...2.1...9..5..4.72..19..3..8..

Update: Created by adding randomly clues and checking each step with HoDoKu I came to 26 clues and a relatively easy puzzle.
After removing 2 clues to minimalize it became extremely hard.

Website · by **denis_berthier** » Mon Apr 19, 2021 4:34 am

.
SER = 8.5. I think few people would consider this as human solvable.

It has nothing remarkable (at least, not that I have seen); it is a typical randomly generated puzzle of SER 8.5. In terms of chains, it is in W6, Z8 or tW8, which means it requires relatively long chains to be solved.

by **urhegyi** » Mon Apr 19, 2021 7:33 am

YZF_sudoku finds an UR forcing chain as hardest step. This is also new to me and appreciate any help to make this understand.

by **yzfwsf** » Mon Apr 19, 2021 7:46 am

urhegyi wrote:YZF_sudoku finds an UR forcing chain as hardest step. This is also new to me and appreciate any help to make this understand.

The UR forcing chain is to find a single chain for each guardian of UR, and the number of common deletions of these single chains is the effective eleminations of this technique. You can press the shortcut key F4 to switch and observe each single chain. You can also directly click on a specific line in the detailed prompt window to observe the corresponding single chain.

by **urhegyi** » Mon Apr 19, 2021 5:09 pm

Last example was to hard.
New try:

Code: Select all: 1.......6.2..3..5....1.4.....42....1.7..5..8.8..4.6..9..9....7..3......5...8..4..

by **urhegyi** » Mon Apr 19, 2021 6:07 pm

And a little change at the center has no influence on 2 of the horizontal bands...

Code: Select all: ........6.2.....5.3..1.4.....43....1.7..5..8.8..4.6..9..9....7............18.34..

by **jco** » Wed Apr 21, 2021 4:52 pm

Hello,

Only now I finished solving the second puzzle (done in parts due to time constraints).
I found a solution in 7 steps (had fun with step 6).
There must be a shorter way, perhaps using that UR earlier (step 4).
To avoid long lines, el. and pl. denote elimination and placement, respectively.

After basics

Code: Select all: .--------------------------------------------------------------. | 1 f89 37 | 57 278 2578 | 2389 4 6 | | 4 2 67 | 679 3 789 | 1 5 78 | |e35679 f5689 3567 | 1 2678 4 | 2389 d239 2378 | |---------------------+-------------------+--------------------| | 3569 56-9 4 | 2 a789 3789 | 57 36 1 | | 2369 7 1236 | 39 5 139 | 236 8 4 | | 8 15 23 | 4 17 6 | 57 23 9 | |---------------------+-------------------+--------------------| | 256 4 9 | 356 126 1235 | 2368 7 238 | | 267 3 8 | 679 4 279 | 269 1 5 | | 2567 156 12567 | 8 b2679 23579 | 4 c2369 23 | '--------------------------------------------------------------'

1. (9)r4c5=r9c5-r9c8=r3c8-(9)r3c1=(9)r13c2 => -9 r4c2 (2 el. by LC and NT)

Code: Select all: .--------------------------------------------------------------. | 1 89 37 | 57 278 2578 | 2389 4 6 | | 4 2 67 | 679 3 789 | 1 5 78 | | 35679 5689 3567 | 1 2678 4 | 2389 239 2378 | |----------------------+-------------------+-------------------| | 359-6 *569 4 | 2 789 3789 | 57 *36 1 | | 2369 7 1236 | 39 5 139 | 236 8 4 | | 8 15 23 | 4 17 6 | 57 23 9 | |----------------------+-------------------+-------------------| | 256 4 9 | 356 126 1235 | 2368 7 238 | | 267 3 8 | 679 4 279 | 269 1 5 | | 257-6 *156 1257-6 | 8 279-6 23579 | 4 *2369 23 | '--------------------------------------------------------------'

2. X-Wing(6) c28 r49 => -6 r9c135, -6 r4c1

Code: Select all: .-------------------------------------------------------. | 1 89 a37 | 57 278 2578 | 2389 4 6 | | 4 2 a67 | 79-6 3 789 | 1 5 78 | | 3567 89 3567 | 1 h2678 4 | 2389 239 2378 | |-----------------+------------------+------------------| | 359 d56 4 | 2 789 3789 |e57 d36 1 | | 2369 7 1236 | 39 5 139 | 236 8 4 | | 8 15 b23 | 4 f17 6 |f57 c23 9 | |-----------------+------------------+------------------| | 256 4 9 | 356 g126 1235 | 2368 7 238 | | 267 3 8 | 679 4 279 | 269 1 5 | | 257 156 1257 | 8 279 23579 | 4 2369 23 | '-------------------------------------------------------'

3. (6=73)r12c3-r6c3=r6c8-(3=65)r4c28-r4c7=(5-71)r6c57=(1-6)r7c5=(6)r3c5 => -6 r2c4 (2 pl., 1 el. by LC)

Code: Select all: .------------------------------------------------------. | 1 89 a37 | 57 278 2578 | 389 4 6 | | 4 2 6 | 79 3 789 | 1 5 78 | | 35-7 89 357 | 1 6 4 | 2389 239 2378 | |-----------------+-----------------+------------------| | 359 56 4 | 2 789 3789 | 57 d36 1 | | 2369 7 123 | 39 5 139 | 236 8 4 | | 8 15 b23 | 4 17 6 | 57 c23 9 | |-----------------+-----------------+------------------| | 256 4 9 | 356 12 1235 | 2368 7 238 | |g267 3 8 | 679 4 279 | 269 1 5 | |g257 f156 f125-7| 8 279 23579 | 4 e2369 23 | '------------------------------------------------------'

4. (7=3)r1c3-r6c3=r6c8-(3=6)r4c8-r9c8=(6-17)r9c23=(7)r89c1 => -7 r3c1,r9c3

Code: Select all: .-----------------------------------------------------. | 1 89 b7-3 | 57 278 2578 |a389 4 6 | | 4 2 6 | 79 3 789 | 1 5 78 | |j35 89 i357 | 1 6 4 | 289-3 29-3 278-3| |----------------+-----------------+------------------| | 359 e56 4 | 2 789 3789 | 57 e36 1 | | 2369 7 g123 | 39 5 139 | 236 8 4 | | 8 f15 c23 | 4 17 6 | 57 d23 9 | |----------------+-----------------+------------------| | 256 4 9 | 356 12 1235 | 2368 7 238 | | 267 3 8 | 679 4 279 | 269 1 5 | | 257 156 h125 | 8 279 23579 | 4 2369 23 | '-----------------------------------------------------'

5. (3)r1c7=r1c3-r6c3=r6c8-(3=65)r4c28-(5=1)r6c2-r5c3=(1-5)r9c3=r3c3-(5=3)r3c1 => -3 r3c789,r1c3
(8 pl., 3 el. by LC)

Code: Select all: .-----------------------------------------------. | 1 9 7 | 5 28 28 | 3 4 6 | | 4 2 6 | 79 3 79 | 1 5 8 | | 35 8 35 | 1 6 4 | 29 29 7 | |----------------+-----------------+------------| | 359 56 4 | 2 789 3789 | 57 36 1 | | 2369 7 123 | 39 5 139 | 26 8 4 | | 8 15 23 | 4 17 6 | 57 23 9 | |----------------+-----------------+------------| | 256 4 9 |b36 1-2 135-2 | 8 7 a23 | | 267 3 8 |c679 4 d279 | 69 1 5 | | 257 156 125 | 8 279 23579 | 4 69 23 | '-----------------------------------------------'

6. UR(79) r29 c46 using internals

(2=3)r7c9-(3=6)r7c4-(6)r8c4==(2)r8c6 => -2 r7c56 (9 pl., 1 el. by LC)

Code: Select all: .-------------------------------------------. | 1 9 7 | 5 28 28 | 3 4 6 | | 4 2 6 | 79 3 79 | 1 5 8 | | 3 8 5 | 1 6 4 | 29 29 7 | |-------------+----------------+------------| | 59 56 4 | 2 89 389 | 7 36 1 | |c69 7 23 |b39 5 1 | 26 8 4 | | 8 1 23 | 4 7 6 | 5 23 9 | |-------------+----------------+------------| | 25-6 4 9 |a36 1 35 | 8 7 23 | | 267 3 8 | 679 4 279 | 69 1 5 | | 257 56 1 | 8 29 23579 | 4 69 23 | '-------------------------------------------'

7. XY-Wing (6=3)r7c4-(3=9)5c4-(9=6)r5c1 => -6 r7c1; ste

Regards,
jco

by **urhegyi** » Thu Apr 29, 2021 4:59 pm

denis_berthier wrote:.
SER = 8.5. I think few people would consider this as human solvable.

It has nothing remarkable (at least, not that I have seen); it is a typical randomly generated puzzle of SER 8.5. In terms of chains, it is in W6, Z8 or tW8, which means it requires relatively long chains to be solved.

From time to time when generating sudoku's I find some examples like the one I posted before and another one:
SER = 8.9:

: computer.png (14.92 KiB) Viewed 625 times

I wonder if there are many human solvers interested in such puzzles.

Code: Select all: 1....8..3..2.9.4...5.........7.4.....6..59.8....2..5....9...1...8..6..2.7....5..4

Website · by **denis_berthier** » Thu Apr 29, 2021 6:03 pm

urhegyi wrote:SER = 8.9
I wonder if there are many human solvers interested in such puzzles.
Code: Select all
1....8..3..2.9.4...5.........7.4.....6..59.8....2..5....9...1...8..6..2.7....5..4

It is in W6 also.
Same remarks as for the previous puzzle: unless it has some hidden characteristic, it is typical of randomly generated puzzles.

The following resolution path can probably be shortened, but it will give you an idea of the rules involved in the solution.

Code: Select all: Resolution state after Singles and whips[1]: +----------------------+----------------------+----------------------+ ! 1 479 46 ! 4567 27 8 ! 2679 5679 3 ! ! 368 37 2 ! 13567 9 137 ! 4 1567 15678 ! ! 34689 5 3468 ! 13467 1237 12347 ! 26789 1679 126789 ! +----------------------+----------------------+----------------------+ ! 5 1239 7 ! 8 4 136 ! 2369 1369 1269 ! ! 234 6 134 ! 137 5 9 ! 237 8 127 ! ! 389 139 138 ! 2 137 1367 ! 5 4 1679 ! +----------------------+----------------------+----------------------+ ! 2346 234 9 ! 347 2378 2347 ! 1 3567 5678 ! ! 34 8 5 ! 13479 6 1347 ! 379 2 79 ! ! 7 123 136 ! 39 238 5 ! 3689 369 4 ! +----------------------+----------------------+----------------------+

Resolution path in W6: Show

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multi steps but still human solvable?

multi steps but still human solvable?

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