The New Sudoku Players' Forum

[markf]

Hi all:
I posted this in a reply and then realized it should have been a new topic. So sorry if someone has already posted a reponse (clearly I'm new to forums or is it fora? Anyway) Here's one I was working on. I actually "solved" it but by accident. Here's where I was....

x86 XX2 4XX
1X7 964 2XX
XX4 X8X 6XX
769 8XX 5XX
X4X X9X 8XX
X18 XX6 7XX
X71 6XX 9XX
XXX 179 3X6
693 428 157

I was able to eliminate 8 as a candiate from r7c8. But I can't make any further inferences. the sudocue program said there was a naked triple in box 3, with 3,5,8 but I thought 3 and 5 could appear in other boxes. I'm confused at the very least. I'm pretty sure if I could fill in one box I could solve it. When I did "solve" it I thought once I had done the elimination I wrote of above then 8 could only appear in the column 8 in row 8. I had somehow forgotten that it could be in r2c8 as well. It worked out but wasn't tremendously satisfying. Any nudges?

Thanks in advance,

Mark

[ChrisT]

I think that the puzzle, as you have posted it, has multiple solutions. Have you missed off one of the original clues?

Chris

[markf]

x86 XX2 4XX
1X7 964 2XX
XX4 X8X 6XX
769 8XX 5XX
X4X X9X 86X
X18 XX6 7X9
X71 6XX 9XX
XXX 179 3X6
693 428 157

Basically I'm an idiot.
actually missed two clues, this after double checking it. thanks. the puzzle above is correct now.

thanks,
mark

[Cec]

"..... Here's one I was working on. I actually "solved" it but by accident.....It worked out but wasn't tremendously satisfying. Any nudges?"

Hi Mark,

It seems you have submitted this puzzle after getting stuck. If that is the case it is suggested for future posts that you submit both the original puzzle plus your part completed puzzle.

The following links provide explanations for basic and advanced solving techniques. In another thread you indicate you are a newcomer so make sure you fully understand the sections describing 'naked' and 'hidden' pairs, triples and 'Locked candidates' (1) & (2) which are sufficient to solve this puzzle.

http://www.angusj.com/sudoku/hints.php
http://www.simes.clara.co.uk/programs/sudokutechniques.htm

The following "nudges" should help if you get stuck:

A 'naked pair' exists in row(r)8 enabling similar candidates to be excluded from this row and box7.

3's are 'locked' in Box4 column(c)1 (refer 'Locked candidates(1)' mentioned above) - this eliminates other 3's in this same column. There is also a situation of 'Locked candidates(2)' in box6 which enables other similar candidates to be excluded from other rows in this same box - try identifying it yourself.

A 'naked triple' exists in c8 which allows other identical candidates to be excluded from this column. The remainder of the puzzle should now unravel by identifying a flood of 'singles'.

Cec

[markf]

thanks cec for the nudges and the posting etiquette suggestions.

Here's what I had gotten it to on my own:

59 8 6 357 135 2 4 1379 135
1 35 7 9 6 4 2 38 385
259 235 4 357 8 1357 6 1379 135
7 6 9 8 134 13 5 1234 1234
235 4 25 2357 9 1357 8 6 123
235 1 8 235 354 6 7 234 9
48 7 1 6 35 35 9 24 248
48 25 25 1 7 9 3 48 6
6 9 3 4 2 8 1 5 7

I had seen the locked pair in box 7 and the locked 3's in box 4. I hadn't seen the locked candidates in box 6 or the naked triple in c8, the contents of which are (1,3,7,9), (3,8) (1,3,7, 9), (1,2,3,4) (6) (2,3,4), (2,4) (4,8), and (5). So doing this I see a hidden pair, the (7,9) which I just missed before. So that locks the 1 into c9 for box 3, and eliminate s1 from r5c5 setting up a naked triple on r5 between r5c1, r5c3, abd r5c5 with the values {2,3,5}. Does that make sense?

What I don't see is the naked triple in c8 or the locked candidates in box 6 (unless it's 1.)

Can you give me some more guidance on that? I appreciate the time you've already spent on this. thanks much.

Mark

[CathyW]

It was the naked pair (7,9) in column 8 that unlocked the puzzle - all singles from there on. I couldn't see a triple in c8 either!!

[emm]

what I don't see is the naked triple in c8 or the locked candidates in box 6

The 2s are locked into r4 in box 6 – this leaves the triple 38, 34, 48 in c8.

I see a hidden pair, the (7,9) ... that locks the 1 into c9 for box 3, and eliminate s1 from r5c5 setting up a naked triple on r5 between r5c1, r5c3, abd r5c5 with the values {2,3,5}. Does that make sense?

Yes it does make sense if you mean r5c9 not r5c5!

It goes to show that there is more than one pathway to the final solution.

[markf]

I see it now, thanks a lot.

Mark

[Cec]

It was the naked pair (7,9) in column 8 that unlocked the puzzle - all singles from there on. I couldn't see a triple in c8 either!!

Hi Cathy, I still can't see there was a "naked" pair (79) in column 8. I've spotted a "hidden"pair (79) in this column (rows1 & 3) but can't see how this unravels the puzzle with all singles?

The triple in column8 only emerges after the following eliminations:
In Box6, the 2's are restricted ("locked in") to r4 which enables all other 2's to be excluded from this Box6. This leaves (3,4) in r6c8. Secondly, the naked pair (2,5) in r8 excludes any other 2's in this row leaving (4,8) in r8c8. With (3,8) in r2c8 we now have a naked triple (348) in column8 (rows2,6 & 8).

There may be a shorter way to solve this puzzle but 'em's comment makes me feel better.

What I don't see is the naked triple in c8 or the locked candidates in box 6 (unless it's 1.)

Hi again Mark - See explanation above for naked triple in c8.

Unless I'm missing something I can't follow your references to "a Locked pair in Box7" or "Locking 1 into c9 for Box3" .

No offence but I'm not sure you understand the principles to identify "Locked candidates"1 and 2 as previously explained in this thread which you might wish to study again. Nevertheless, I will try to explain the "Locked Candidates 2" situation in Box6.

Look at row4 and you will see that candidate 2's appear only in the top row of Box6. As each row (and column and box) can only contain each digit 1 to 9 then candidate 2 for box6 must be in r4. Although we don't yet know which of the two cells the 2 will go in this row (either r4c8 or r4c9) what we do know is that any other candidate 2's in Box6, other than those in r4, can safely be excluded. This therefore excludes the 2's in r5c9 and r6c8.

I know the sinking feeling I get when readers pick up my typing mistakes because this makes it difficult to get your message across and probably frustrate readers. I know it takes more time but I preview my replies, usually twice, and again read them when they appear in the forum. Now I'm really sticking my neck out hoping this reply is without errors!

Cec

[markf]

Cec,
No offence taken.

I'm on the road to understanding the principal, and follow your explanation and em's. I just looked at the puzzle too long and looked at the columns instead of looking at the rows. I'm not pleased with that by the way, but so it goes.

Again I appreciate the time you spent checking my work. Especially when I made it more difficult by littering it with typos.

In terms of the pair 7,9 in box 3, once that was spotted and the 1's in column 9 were eliminated as candidates from box 6, a fairly easy to see naked triple was apparent in row 5 of 2,3,5 (I write easy because I saw it) which led to a fast conclusion as well.

Boy, I hope there are no mistakes in this post.

Best,
Mark

[Cec]

"....In terms of the pair 7,9 in box 3, once that was spotted and the 1's in column 9 were eliminated as candidates from box 6, a fairly easy to see naked triple was apparent in row 5 of 2,3,5 (I write easy because I saw it) which led to a fast conclusion....."

Mark, there is still confusion and I may have to appeal for a third umpire to confirm my following thoughts:

The (79) pair in Box 3 (ie. cells r1c8 and r3c8) only eliminates candidates 1 and 3 from these two cells - I can't see how you exclude other candidate 1's from column9 and from Box 6.

My previous post explained how candidate 2's are "locked" in r4c8 and r4c9 (Box6) which only eliminates the other 2's in this box - it does not eliminate candidate 1's either from this box or from column9.

I can't identify 'your' naked triple(235) in row5 because these three numbers either wholly or partly occupy five cells in this row. This thread better explains the criteria for triples which must be restricted to only three cells.

It looks like more homework Mark?

Cec

[emm]

Hi Cec, I don’t play cricket – can I be the 3rd umpire?

The 7,9 pair eliminates 1 from r1c8 and r3c8
=> 1s are locked into column 9 in box 3
=> eliminate 1s from column 9 box 6
=> a triple 235,25,3 in row 5

In a way funny to see this as triple when there’s a naked single, but hey - does it really matter if all roads lead to Rome!

[masb]

I don't play cricket either but my solution is:

Code: Select all

Pair Row @ r7c5 r7c6 r8c2 r8c3> r7c1x5 r8c1x2 r8c1x5 r8c8x2
Pair Box @ r8c2 r8c3> r7c1x2
Box Column @ 4> r1c1x3 r3c1x3
Row Box @ 4> r5c9x2 r6c8x2
Triple Column r1c8x3 r3c8x3 r4c8x3 r4c8x4 r7c8=2 r2c9=8 r4c9x1 r4c9x3
Single r2c8=3 r4c8=1 r7c9=4
Single r2c2=5 r4c6=3 r4c9=2 r5c9=3 r6c8=4 r7c1=8 r8c8=8
Single r1c1=9 r4c5=4 r6c5=5 r7c6=5 r8c1=4 r8c2=2
Single r1c8=7 r3c1=2 r3c2=3 r6c4=2 r7c5=3 r8c3=5
Single r1c5=1 r3c8=9 r5c1=5 r5c3=2 r5c4=7 r6c1=3
Single r1c9=5 r3c4=5 r3c6=7 r5c6=1
Single r1c4=3 r3c9=1

Where the only tricky bit is the 348 tripple in column 8 and the 135 tripple in column 9. The codes above mean x to remove a candidate and = is set to value. @ indicates reference cells or boxes and > is the resulting action. I did cheat a bit and use my program for this http://www.axcis.com.au/bb/viewtopic.php?t=25).

Yet another road to Rome...

[Cec]

Hi Cec, I don’t play cricket – can I be the 3rd umpire?

No! because you 'catch' people out too well. I've now completed my homework and I'm pleased Mark also spotted this further example of "Locked Candidates 2" in Box3 which I missed. Thanks 'em' and 'masb' for your prompt replies. Way past my bedtime now so I'll follow masb's effective presentation tomorrow of solving this puzzle

Cec

[Cec]

"I don't play cricket either but my solution is (See above post)..."

Thanks again masb for your response.
I grasped your above presentation technique fairly quickly. It eliminates the general forum opposition of publishing the complete solution (which I agree provides no useful help to the reader) - with your technique one has the choice to resume solo at any time and only revert back to your 'guide' for further hints when stuck. Then again, this is only my opinion.

" ..Boy, I hope there are no mistakes in this post"

There weren't but there was in mine. Pleased to see you now understand "Locked Candidates". The difficulty I still find is to spot them.

Cec