Just to correct it, I think you meant naked pair of 3,6

hoo no again typo

Thank You.

Sudoku Surprise - What an amazing test with a great set of sudokus.One of those tests which I felt had that rare 'reunion'of sorts between sudokus and puzzles.Rather than reflecting on my performance which was sub-optimal,I thought it would be prudent to get down to brass tacks and try understanding the beautiful intricacies hidden in each puzzle.

So,I came across this Secret Code sudoku which I attempted during the test and spent close to an hour!! on this single puzzle and still could not get to the solution (logically).I guessed the answer key knowing that it had to contain one of these strings 2316,2361,3216,3261 in Column 3 .Once again ,it turned out to be a lucky guess .Hence to be candid, it's only 470 points that I could muster in reality.
The reason that I am posting this here is that 80% of the solvers should have reached the following stage after which they would have hit a dead-end.The Sudoku could not have become more stuck.
So fellas,if someone did find that devastating piece of logic from this point which brings the curtains down on this one ,I would be glad to know.

----Kishore-----


Edited by kishy72 2014-11-26 4:40 PM

I guess everyone was stuck for sometime at this point.
Firstly if you see the arrows which are least pointing directions:eg r6c1 or r1c3 they can point at most 3 directions.
Now the logic i used is if you see 2-3 pair, for the solution to become unique atleast one of 2 or 3 has to be part of secret code. So this restricts further the direction of r6c1 and it has to be pointing right. (This way i got one direction - so atleast now i know that secret code belongs to order which will follow row 6 and it has atleast one of 2 or 3 and it can't be 3rd digit of the code)
This immediately fixes the direction of r3c9 which has to be towards r4c8. Also this implies that secret code cannot contain 4,5,8.
Now this gives that r2c4 arrow has to be towards right or towards r3c5. But now if its towards r3c5 then it has to be 376 due to obvious reasons. but this is not possible immediately you can check that with known arrow directions i.e row 6. So r2c4 arrow is pointing right. which implies code is 371 (as 4 is not part of it and 2 cannot be as it is last).

Hope this helps. I don't know if above is right way or not. But would still love to know if any other shorter way is there :)

*sorry small edit in above r6c1 can be 4 directions but anyways that doesn't change the analysis :)

Excellent!I think that you have provided the precise logical way of solving this sudoku.I seriously doubt if there is a shorter way than the above mentioned one.
Right at step 1 ,I faltered.I mean,I failed to deduce that, atleast one of 2 or 3 has to be part of the code as it did not hit me that the puzzle would fail to be unique without that.Tremendous!!!
Also, I understand that the most important strategy to adopt in this puzzle is to concatenate clues and see if they work in conjunction with other clues.These are the grey areas that needs to worked on.
Thanks a lot for the explanation.Well done !!

Hi all!!I was randomly solving some sudokus from the IB of Swiss Team Qualification round when I came across this Arrow-thermo sudoku .I fail to see a logical continuation from the following point....Can someone spot the same and share .....



Edited by kishy72 2015-06-02 6:07 PM

R5C3 and R7C3 contain (3,5). So, R6C3 = 7, and R1C3 = 6 ......
From here, it can be solved forward.

Advised only seeing just plainly, not gone through whole.. Maybe wrong also

There is also possibility of 3 in R3C3/R3C6.So your deduction is not correct.

7 can only come at R3C9 or R5C9

if you put 7 at R5C9, then 9 is forced at R6C8
which will force 9 at R5C2, this will force 9 at R3C1.

9 at R3C1 will force 9 at R2C8, which is wrong as R6C8 already contains 9

so 7 should come at R3C9.
It should be easy solve from there on.

Somewhat similar to gaurav but a 2 step smaller,

Consider 1,3,4,6 boxes. Each has only 2 or 3 places of placing 9. So visually its easy to see that placing 9 at r3c7 leaves no room to place 9 in box 4. After this its easy i suppose.

Interesting ways of looking at the logic for the same outcome.The first appears to be a bit of a hit and trial and the second approach is shorter but much more difficult and global/broader thinking is required.Nevertheless the latter seems the ideal way for dealing with the issue aptly.So then I assume that there is no other shorter logical path than the ones mentioned.Thanks a lot for sharing the logic ....Gaurav and Swaroop

Kishore

Stuck in this combo variant.Anti-knight + Renban.Same numbers are not chess knight-move connected and all groups of connected cells form consecutive numbers.I know it is not one of those regular sudokus that we get to solve most of the time.But still,it is that long chain of logical thinking and visualization required before hitting a contradiction in these kind of variants that fascinates me and induced me to solve these......

Source and Author Credits : Logic masters deutschland / Zhergan




Edited by kishy72 2015-06-11 7:11 PM

7 will be in r7c5 because in box 5 , 7 can only come at r4c6, r6c6, r6c4 eliminating 7 from r7c6. After this even I am stuck

I am afraid but I don't see how you eliminated 7 from R6C5?!If you consider that case 7 may in fact be in R7C6

I'm not sure if the cross you made for R9C4 is to denote that 8 cannot be there, but I assume so (because it is true that it can't be there, you'll reach a contradiction placing an 8 in C3). This means there's a 7-8 pair in C4 in R2 and R6, which gives a 9 in R4C4.

Indeed!Thanks a lot!!It was close to impossible finding that 78 pair amidst that clutter.It looks almost invisible to the human eye.I got to add here that this sudoku is in no way trivial and tremendously sticky even after using this deduction .I would advise anyone interested to have a go at it seriously and give themselves a pat after completion.I completed it just before and the solving experience and the satisfaction of completion was like nothing before.

Thanks again prasanna for setting the direction in the right path in the above sudoku!

Seriously deadly sudoku, even after placing that 9 i am not sure if there is any simplified steps.

I was trying to solve this Search 9 Sudoku on Fed-Sudoku and am stuck at this point. I don't know how to proceed further. Can anyone give a hint? Have I made any mistake?



Edited by aashay 2015-06-21 11:44 PM

There is a mistake in your solve.Look at the 3 clue in R5C3.You have a 9 in R6C4 which violates that.You have gone wrong somewhere in between....

Edited by kishy72 2015-06-22 1:14 AM

It may not be wrong - the rules are different on the Fed series. All possible arrows are given where a digit points towards a 9 at that distance away from it, so it is very different from the ISC one.

I also thought the same, so I reset it and solved again from scratch, but reached the same point.

What you are missing is the "all possible arrows are marked" of this puzzle. What you have solved so far mostly isn't wrong but there is an extra rule here which isn't in the ISC one - if there is say a 3 in a cell without an arrow, there cannot be a 9 three cells away from that 3 in any direction (I repeat, this is NOT a rule for the ISC one)

Please Classics vs. Innovatives IB & PB for extra practice material for Search 9 with exact rules.