The New Sudoku Players' Forum

by **champagne** » Wed Nov 05, 2025 8:46 am

as noticed "gfick", this one is not trivial, but with potential for skill solvers

pm at start

Code: Select all: |++++++++++++++++++++++++++++++|++++++++++++++++++++++++++++++|++++++++++++++++++++++++++++++| | 9 8 13 | 7 1245 12345 | 6 245 125 | | 5 17 4 | 6 128 12 | 3 2789 12789 | | 1367 2 136 | 134 9 1345 | 157 4578 1578 | |++++++++++++++++++++++++++++++|++++++++++++++++++++++++++++++|++++++++++++++++++++++++++++++| | 2346 5 2369 | 2349 2467 8 | 279 1 23679 | | 12368 1369 7 | 5 126 1239 | 4 289 23689 | | 123468 13469 12369 | 12349 12467 12349 | 2579 25789 2356789 | |++++++++++++++++++++++++++++++|++++++++++++++++++++++++++++++|++++++++++++++++++++++++++++++| | 1247 1479 8 | 1249 1245 6 | 12579 3 12579 | | 1237 1379 12359 | 8 125 1259 | 12579 6 4 | | 1246 1469 12569 | 1249 3 7 | 8 259 1259 | |++++++++++++++++++++++++++++++|++++++++++++++++++++++++++++++|++++++++++++++++++++++++++++++|

98.7..6..5.46..3...2..9.....5...8.1...75..4.............8..6.3....8...64....378..

by **champagne** » Wed Nov 05, 2025 6:49 pm

One clue to start

In the solution grid 1259r8c56 and 1259r9c89 have the four digits 15r8c56 29r9c89

This is usually a start for a DJE, but here, it works for digits 259, not for the digit 1.

Is it possible using this partial DJE to establish that we have the right pattern in the solution grid and to use some of the properties of a double DJE??

by **champagne** » Thu Nov 06, 2025 9:07 am

Code: Select all: 9 8 13 |7 1245 12345 |6 245 125 5 17 4 |6 8 12 |3 279 1279 1367 2 136 |134 9 1345 |157 4578 1578 ---------------------------------------------------------- 2346 5 2369 |2349 2467 8 |279 1 23679 12368 1369 7 |5 126 1239 |4 289 23689 123468 13469 12369 |12349 12467 12349 |2579 25789 2356789 ---------------------------------------------------------- 1247 1479 8 |1249 1245 6 |12579 3 12579 1237 1379 12359 |8 125 1259 |12579 6 4 1246 1469 12569 |1249 3 7 |8 259 1259

It seems that nobody is ready to come with a solution, so I do the first step.

Having a partial DJE for the digits 259, we know that they cannot be more than once in the 2 bases r8c56 r9c89 (each base sees the 2 targets of the other)
So at least one ‘1’ must be there, but I see no direct way to exclude one ‘1’ in each base.
We have to show that this is not possible. I’ll do it in several steps to make it easier to the reader to follow

Assume ‘1’ in both bases some needed cleanings and 1r3c7 assigned

Code: Select all: 9 8 13 |7 1245 12345 |6 245 125 5 17 4 |6 8 12 |3 279 1279 1367 2 136 |134 9 1345 |1* 4578 1578 ---------------------------------------------------------- 2346 5 2369 |2349 2467 8 |279 1 23679 12368 1369 7 |5 126 1239 |4 289 23689 123468 13469 12369 |12349 12467 12349 |2579 25789 2356789 ---------------------------------------------------------- 1247 1479 8 |249 245 6 |2579 3 2579 1237 1379 2359 |8 125 1259 |2579 6 4 1246 1469 2569 |249 3 7 |8 259 1259

Bivalues chain easy to reach

Code: Select all: 9 8 1* |7 1245 12345 |6 245 125 5 17 4 |6 8 12 |3 279 1279 367 2 36 |34 9 345 |1* 4578 1578 ---------------------------------------------------------- 2346 5 2369 |2349 2467 8 |279 1 23679 12368 1369 7 |5 26 1239 |4 289 23689 123468 13469 2369 |1* 2467 12349 |2579 25789 2356789 ---------------------------------------------------------- 1247 1479 8 |249 245 6 |2579 3 2579 1237 1379 2359 |8 125 1259 |2579 6 4 1246 1469 2569 |249 3 7 |8 259 1259

Hidden pair 36 r3c13

Code: Select all: 9 8 1* |7 1245 12345 |6 245 125 5 17 4 |6 8 12 |3 279 1279 367 2 36 |4* 9 5* |1* 4578 1578 ---------------------------------------------------------- 2346 5 2369 |2349 2467 8 |279 1 23679 12368 1369 7 |5 26 1239 |4 289 23689 123468 13469 2369 |1* 2467 12349 |2579 25789 2356789 ---------------------------------------------------------- 1247 1479 8 |24-9 4* 6 |2579 3 2579 1237 1379 2359 |8 125 1259 |2579 6 4 1246 1469 2569 |24-9 3 7 |8 259 1259

No solution for the hidden pair 15 in column 5 we have a full DJE in the bases r5c7=7 r9c4=4

Code: Select all: 9 8 13 |7 1245 12345 |6 245 125 5 17 4 |6 8 12 |3 279 1279 1367 2 136 |13 9 1345 |15 4578 1578 -------------------------------------------------------- 2346 5 2369 |239 2467 8 |29 1 23679 12368 1369 7 |5 126 1239 |4 289 23689 123468 13469 12369 |1239 12467 12349 |259 25789 2356789 -------------------------------------------------------- 47 47 8 |129 125 6 |1259 3 1259 123 139 12359 |8 125 1259 |7 6 4 126 169 12569 |4 3 7 |8 259 1259

The rating falls to skfr 8.5 but with still some potential to do more with this partial DJE

by **Cenoman** » Thu Nov 06, 2025 8:31 pm

champagne wrote:It seems that nobody is ready to come with a solution,

You left us too less time... :!:

My solution is based on General Exocets:
Note: I have doubts about digit 5 complying with JE pattern (because of the given 5r5c4, in cross-line c4...)

Code: Select all: +---------------------------+--------------------------+----------------------------+ | 9 8 13 | 7 1245 12345 | 6 245 125 | 1 | 5 17 4 | 6 8 12 | 3 279 1279 | | 1367 2 136 | 134 9 1345 | 157 4578 1578 | 1 5 +---------------------------+--------------------------+----------------------------+ | 2346 5 2369 | 2349 2467 8 | 279 1 23679 | 2 9 | 12368 1369 7 | 5 126 1239 | 4 289 23689 | 5 | 123468 13469 12369 | 12349 12467 12349 | 2579 25789 2356789 | 1 2 5 9 +---------------------------+--------------------------+----------------------------+ | 47-12 47-19 8 | T129-4 1245 6 | t129-57 3 12579 | | 1237 1379 T125-39 | 8 b125 b1259 | 7-1259 6 4 | | 1246 1469 t1259-6 | 1249 3 7 | 8 B259 B1259 | +---------------------------+--------------------------+----------------------------+

Double General Exocet (1259)r8c56, r9c3, r7c7; r9c89, r7c4, r8c3
Check the exocet property:
- for digit 1: +1r8c56, -1r9c3, -1r7c7 => no solution (with singles); +1r9c89, -1r7c4, -1r8c3 => no solution (with singles)
- for digit 5: +5r8c56, -5r9c3, -5r7c7 => box 7 void of 5's; +5r9c89, -5r7c4, -5r8c3 => box 7 void of 5's
- for digits 2, 9: they comply with the JE requirement

Eliminations:
-4r7c4, -7 r7c7, -3r8c3, -6r9c3 (non base digits in target cells);
-1259r8c7, -129r7c12 (cells in sight of the 4 base cells or the 4 target cells)
-5r7c7, -9r8c3 (base digits in target cells, false in mirror nodes)

Resulting resolution state (skfr 8.5):

Code: Select all: +---------------------------+-------------------------+--------------------------+ | 9 8 13 | 7 1245 12345 | 6 245 125 | | 5 17 4 | 6 8 12 | 3 279 1279 | | 1367 2 136 | 13 9 1345 | 15 4578 1578 | +---------------------------+-------------------------+--------------------------+ | 2346 5 2369 | 239 2467 8 | 29 1 23679 | | 12368 1369 7 | 5 126 1239 | 4 289 23689 | | 123468 13469 12369 | 1239 12467 12349 | 259 25789 2356789 | +---------------------------+-------------------------+--------------------------+ | 47 47 8 | 129 125 6 | 129 3 1259 | | 123 139 125 | 8 125 1259 | 7 6 4 | | 126 169 1259 | 4 3 7 | 8 259 1259 | +---------------------------+-------------------------+--------------------------+

Solution in 6 steps (AICs and one kraken)

Hidden Text: Show

by **champagne** » Thu Nov 06, 2025 9:01 pm

Cenoman wrote:Check the exocet property:
- for digit 1: +1r8c56, -1r9c3, -1r7c7 => no solution (with singles); +1r9c89, -1r7c4, -1r8c3 => no solution (with singles)

Hi Cenoman;
I likely have no problem with the rest of your path.
For digit '1', 'gfick' warned me that the DJE did not work and yes, the solution grid has r1c3='1'.

So, the "exocet check cannot work in any of the base for the digit 1. Each of the 2 bases has a target in column 3.
Something is wrong in your sentence.

IMO the check that the '1' cannot be in both bases is unavoidable.

BTW, I sent him several potential DJE, He has seen in the second one a similar problem, but I did not dig in it.

by **Cenoman** » Thu Nov 06, 2025 10:13 pm

champagne wrote:
Cenoman wrote:Check the exocet property:
- for digit 1: +1r8c56, -1r9c3, -1r7c7 => no solution (with singles); +1r9c89, -1r7c4, -1r8c3 => no solution (with singles)

Hi Cenoman;
I likely have no problem with the rest of your path.
For digit '1', 'gfick' warned me that the DJE did not work and yes, the solution grid has r1c3='1'.

So, the "exocet check cannot work in any of the base for the digit 1. Each of the 2 bases has a target in column 3.
Something is wrong in your sentence.

IMO the check that the '1' cannot be in both bases is unavoidable.

BTW, I sent him several potential DJE, He has seen in the second one a similar problem, but I did not dig in it.

Hi champagne,
May be you have read a bit too fast my post. I'm not claiming DJE pattern, but 'DGE' pattern (Double General Exocet)
I'm back to the 'old' definition of an exocet, the one you recommanded to me long ago here, namely:

Step 1 check that this is an exocet pattern for each digit
a) forces the digit in the base,
b) clear the digit in the target
c) check that you have no solution

Step 2 clear step by step non valid pairs using the exocet property

I'm just applying to digit 1 the three sub-steps a,b,c to conclude that both potential exocets are actual exocets.
As these exocets are in the same band, all eliminations based on base cells, target cells, and mirror nodes are valid.

by **blue** » Thu Nov 06, 2025 11:05 pm

Since it's a double exocet, and since digits 2 & 9 have the JExocet property, these eliminations are also justified: -2r4c159, -2r6c15689, -9r4c9, -9r6c2689

champagne wrote:The rating falls to skfr 8.5 but with still some potential to do more with this partial DJE

Cenoman wrote:Resulting resolution state (skfr 8.5):

I'll bite: how do I get SKFR to rate a PM puzzle ?

Sudoku Explainer rates it at 8.9 -- with or without the extra eliminations.

by **Cenoman** » Thu Nov 06, 2025 11:44 pm

blue wrote:Since it's a double exocet, and since digits 2 & 9 have the JExocet property, these eliminations are also justified: -2r4c159, -2r6c15689, -9r4c9, -9r6c2689

champagne wrote:The rating falls to skfr 8.5 but with still some potential to do more with this partial DJE

Cenoman wrote:Resulting resolution state (skfr 8.5):

I'll bite: how do I get SKFR to rate a PM puzzle ?

Sudoku Explainer rates it at 8.9 -- with or without the extra eliminations.

Hi blue,
I agree with your extra eliminations. I missed them. Rating remains 8.5 with.
To rate a PM puzzle, at any resolution state, I use YZF_Solver (running under MS-Windows OS) Just copy and paste the PM.

by **champagne** » Fri Nov 07, 2025 2:32 am

blue wrote:Since it's a double exocet, and since digits 2 & 9 have the JExocet property, these eliminations are also justified: -2r4c159, -2r6c15689, -9r4c9, -9r6c2689

champagne wrote:The rating falls to skfr 8.5 but with still some potential to do more with this partial DJE

Sudoku Explainer rates it at 8.9 -- with or without the extra eliminations.

Hi blue,

on my side, the answer is easy; I add the new clues to the puzzle and I redo the rating,
I noticed in this puzzle a significant deviation SKFR versus Sudoku Explainer so my 8.5 could be 8.9 using sudoku explainer

by **champagne** » Fri Nov 07, 2025 2:41 am

Cenoman wrote:
Hi champagne,
May be you have read a bit too fast my post. I'm not claiming DJE pattern, but 'DGE' pattern (Double General Exocet)
I'm back to the 'old' definition of an exocet, the one you recommanded to me long ago here, namely:
Step 1 check that this is an exocet pattern for each digit
a) forces the digit in the base,
b) clear the digit in the target
c) check that you have no solution

I fully agree with this and I applied it after the warning or "gfick"

Here is my result with the '1' PM as start

Code: Select all: ..1 .11 ..1 .1. ..1 ..1 1.. 1.1 1.1 ... ... .1. 11. .11 ... 111 111 ... 11. 11. 1.1 111 .11 1.. 111 1.. ..1

for the r9c89 base this gives

Code: Select all: ..1 .11 ... .1. ..1 ... ... ... 1.. ... ... .1. 11. .11 ... 111 111 ... 11. .1. ... 11. .11 ... ... ... ..1

I cannot show that this has no solution; worse, if I set 1r1c3 as in the final solution grid I am here

Code: Select all: ..1 ... ... ... ..1 ... ... ... 1.. ... ... .1. 11. ... ... ... 1.. ... 11. .1. ... 11. .1. ... ... ... ..1

still with several solutions

!!!!

by **champagne** » Fri Nov 07, 2025 2:48 am

blue wrote:Since it's a double exocet, and since digits 2 & 9 have the JExocet property, these eliminations are also justified: -2r4c159, -2r6c15689, -9r4c9, -9r6c2689

I have to go back in my work on it, but using the exocet properties, it seems easy to show that '1' cannot be in r9c89
Same for '5'
then the bases are proven 15 29 and the solution path becomes easier

by **blue** » Fri Nov 07, 2025 4:44 am

champagne wrote:
Cenoman wrote:
Hi champagne,
May be you have read a bit too fast my post. I'm not claiming DJE pattern, but 'DGE' pattern (Double General Exocet)
I'm back to the 'old' definition of an exocet, the one you recommanded to me long ago here, namely:
Step 1 check that this is an exocet pattern for each digit
a) forces the digit in the base,
b) clear the digit in the target
c) check that you have no solution

I fully agree with this and I applied it after the warning or "gfick"

Here is my result with the '1' PM as start

(...)

still with several solutions

You need to use more than just the 1's PM.
For both base/target sets, after clearing target 1's and 1's that can see the base cell 1's, this sequence leads to a conflict/contradiction:

column single 1r3c7
column single 1r6c4
column single 1r1c3
row single 3r1c6
cell single 4r3c4
cell single 5r3c6
box single 4r7c5
column single 5r8c5
--> no candidate for 1 in c5

by **champagne** » Fri Nov 07, 2025 7:09 am

Hi blue,

No doubt, you have several ways to show that the partial exocet can be pushed to the "DJE equivalence" in the 2 bases
But you stay out of the full exocet logic.

In this specific case, as no '1' occupy a target cell of the base, this is equivalent to a direct elimination of 1r9c9.
So it is in some way a variant of my proposal. As one base must have a '1', we have shown that it cannot be both.

The key point IMO is that in such a situation, with each base seing the 2 targets of the other base, you can apply the powerfull cleaning of the cells seing the 2 bases.

EDIT agreed that my final status can be reached using singles as in your sequence.

by **champagne** » Fri Nov 07, 2025 10:34 am

a quick summary where we are

this puzzle has an almost DJE
(1259)r8c56, r9c3, r7c7; r9c89, r7c4, r8c3
it works for 3 digits (259) and each base sees the 2 targets of the other base.

so the digit '1' must be in at least in one of the bases

Following blue chain of singles, we can clean 1 r9c9 forcing 1r8c56 and 259 in base and targets of r9c89

So the bases have the classical pattern of a double DJE r8c7=7 r9c4=4
after some "easy cleaning", we should be in something as

Code: Select all: 9 8 13 |7 1245 12345 |6 245 125 5 17 4 |6 8 12 |3 279 1279 1367 2 136 |13 9 1345 |15 4578 1578 -------------------------------------------------------- 2346 5 2369 |239 2467 8 |29 1 23679 12368 1369 7 |5 126 1239 |4 289 23689 123468 13469 12369 |1239 12467 12349 |259 25789 2356789 -------------------------------------------------------- 47 47 8 |29 25 6 |1259 3 1259 23 39 259 |8 125 1259 |7 6 4 126 169 1259 |4 3 7 |8 259 259

now a relatively easy code.

after a warning from "gfick", this puzzle could have something similar

98.7..6..7...8..9......9...65...84.....5....3...4.....5.2.....6.9..5.7...61..7.4.

by **blue** » Fri Nov 07, 2025 8:13 pm

champagne wrote:a quick summary where we are

this puzzle has an almost DJE
(1259)r8c56, r9c3, r7c7; r9c89, r7c4, r8c3
it works for 3 digits (259) and each base sees the 2 targets of the other base.

so the digit '1' must be in at least in one of the bases

Following blue chain of singles, we can clean 1 r9c9 forcing 1r8c56 and 259 in base and targets of r9c89

The singles chain doesn't work unless you clear the 1's in the target cells before starting it.
Regarding 1r9c9: It doesn't show that "1r9c9 can't be true", it only shows that "it can't be the case that 1r9c9 is true, and both 1r8c3 and 1r7c4 are false".

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