dailysudoku.com

[crunched]

I thought todays puzzle-hard-was especially tough for a non-vh puzzle.

[cgordon]

Agreed!!! Every now and then a “Hard” one pops up that is harder than most “VHs”. The problem is that “Hard” ones shouldn’t require advanced techniques such as ERs, URs or wings. So for these sudokus I only use my basic and primitive skills – just like Rambo. Probably more like Mr Bean – cos right now I’m stuck.

[stevieboy]

OK gang...here goes:

Since I don't know (yet) how to show the puzzle on my replies , I will try to describe, slowly, what I did to solve this puzzle. Again, I didn't do ANY xy-wings, UR's, etc. etc. I used the M-Wing method (Chapter 3) from the same link I referred to earlier:

http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=2143

(And), again, I used the SAME solving method I used in the vh of May 8 to solve that one...I will show you of all the "Strong Links" (ie, a pair along a Row or Column) that I used to solve this one correctly;
after basic eliminations, I did the following:

1. (First Strong Link) R9C4 TO R9C6 -> the STRONG LINK is '7'
2. (Second Strong Link) R9C6 To R4C6 -> the STRONG LINK is '7'
3. (Third Strong Link) R4C6 To R4C7 -> the STRONG LINK is '6'

...so the common cell for R9C4 and R4C7 is cell R9C7

R9C4 contains candidates '1 4 7'
R4C7 contains candidates '1 4 6'

USING THE M-Wing Rule of Chapter 3, we can then eliminate TWO(!!) COMMON CANDIDATES in R9C7 ---> '1' and '4' !!!!

THERE ARE A CRAPLOAD OF M-WINGS (or other facsimiles) IN THESE
SUDOKU'S...AND, THEY'VE ALL BEEN WORKING FOR ME!!

This was actually a trial for me, to see if a Double Candidate-Elimination would work...and, this one passed the test!

I may never have to use another xy-wing, etc. etc., if I don't have to

This is it (maybe?)...and, it REALLY is easy!! (Stevieboy says excitedly!)[/url]

[A.J.]

I used the Block/Block interaction technique on this one. After the basics, if you look at blocks 4 and 6 you notice that 1s appear in only rows 4 and 6 in these two blocks. Therefore one of these blocks must have a 1 in row 4 and the other in row 6. Hence, all 1s can be eliminated in rows 4 and 6 in block 5. It falls out with basics after that.

[Marty R.]

[stevieboy]

Thanks, Marty.

Since I've been doing these puzzles on paper, I just haven't taken the time to transfer them online.

[stevieboy]

Thanks, Marty.

Since I've been doing these puzzles on paper, I just haven't taken the time to transfer them online.

[stevieboy]

Thanks, Marty.

Since I've been doing these puzzles on paper, I just haven't taken the time to transfer them online.

[cgordon]

A.J. Right off the bat there are a pair of 12's in Box 5 (R5C46). This means there can be no other 1's or 2's in Box 5 or Row 5. The rest of the puzzle can be solved by similar line/box eliminations. Though in this one it's hard to find the pairs and triples - I actually got stuck before spotting a single <3> (in Box 1 I think). But wings (including M wings Stevieboy) are definitely not needed for the hards.

[stevieboy]

...that may be true, cgordon, but not long after I did the same stuff you guys did (the 1-2 combo in Box 5 Row 5, which eliminated a lot of stuff in that area), I did the M-Wing, and we were in business...! Since I already had 2 candidates in most of the cells, this one was solved in minutes.

Hard, or very hard - it's sometimes hard to tell the difference.

[kermitbone]

I am still stuck on this one. I guess I still need a little help with the M-Wing. I was able to find the 12 double and the 67 double in box 5, but that didn't solve the puzzle for me.

This is where I am stuck
[

[kermitbone]

Looking at my own post, I see the 13 double in Column 1 which should help me significantly. As far as the M-Wing, was I just not able to see it, because I hadn't gotten the 13 double yet?

I am getting there...

Thanks,

[storm_norm]

the naked pair in row 5 helps a lot in the image above. removes all the 1's and 2's they can see.



the {1,3} naked pair opens up and it should be smooth from there.

at this point you can solve it if you pay close attention to the singles in rows and boxes etc.

[crunched]

I solved this with no wings of any kind, and no URs, or ERS. Line or box line reductions were required. Maybe a naked quad, but can't remember for sure. But indeed this sucker was tough.