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Mogulmeister · Joined: 03 May 2007 Posts: 1151

Interestingly, after the x-wing on 5s you are left with another one of Ted's "almost" xy wings.

There is a fin, 1 in r7c2 preventing the nice XY Wing 459 in r7c28 and r3c8 (in green).

If the 1 is false then the XY wing is true and 9 is eliminated from r3c2 solving the puzzle.

If the 1 is true then r7c1=4 => r7c8=5 => r3c8=9 and so again r3c2 <> 9 also solving the puzzle.

The other plus of course is that you don't have to take Danny's hint ! Wink

(Of course the fin could never be true because if it was, there would be no 9's in column 2!)

daj95376 · Joined: 23 Aug 2008 Posts: 3854

Mogulmeister, your solution is an ALS XY-Wing (from what I can tell).

After studying your cells, this crazy thought popped into my head that you might have an ALS in conjunction with an XY-Wing. So, I went to Sudopedia and checked into the definition of the ALS-XY-Wing, which I've never used.

Sure enough, your cells work as an ALS-XY-Wing.

ALS_A: r3c8=59
ALS_B: r7c12=149
ALS_C: r7c8=45

r7c8=5 + ALS_A => r3c8=9
r7c8=4 + ALS_B => r7c2=9

your elimination follows

Aaack!!! I can't ever again claim that I never used an ALS-XY-Wing. Crying or Very sad

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Of course ! Thanks Danny - 5 is the restricted common and 9 is the other common candidate.

So how many of these "almost" or finned xy wings are going to fall into this category ?

Mogulmeister · Joined: 03 May 2007 Posts: 1151

I think it may just be an ALS XZ since it only uses 2 ALS's..?? Question

The definition in sudopedia posits 3 ALS's but I am in murky water now......

daj95376 · Joined: 23 Aug 2008 Posts: 3854

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Blimey!! See what you mean !

Marty R. · Posted: Thu Apr 22, 2010 5:00 am Post subject:

I used:

X-Wing (5)
XY-Wing (139)
XYZ-Wing (134)
XY-Chain
XY-Wing (459), flightless with pincer transport

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Danny,

How about

ALS_A: r3c8=59
ALS_B: r7c128=1459

Restricted Common = 5 and Common Candidate 9 removed from r3c2 as it sees the 9 in both set A & B ? But what is it called ??

Thanks and apologies for the spaghetti! Could this pattern fall into more than 1 ALS category ?

daj95376 · Joined: 23 Aug 2008 Posts: 3854

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Yes Indeed. But what if looking at finned xy's yields an ALS more frequently than we might suppose. I notice Peterj seems to have another one in your other "fiery" puzzle (which I have not looked at yet).

Locating them is quite difficult but again I imagine there is an algorithm that could do it and I wouldn't mind bétting my house on step 1:

"Look for a bivalue". Laughing

Luke451 · Posted: Thu Apr 22, 2010 5:23 pm Post subject:

I'm not going to be much help in naming patterns and the ABCs of ALS because I see all ALS usage as the same thing: as AICs. Even ALS-xz. They're all AICs to me.

An ALS can appear at the beginning of a chain. It can appear at the end. It can appear at the beginning and the end. It can appear at the beginning, the end, and five times in between. What would scare me is trying to give a name to too many of the countless variations, or identify all the restricteds/commons/A_B_C_sets within a chain that uses ALS.

I like Mogul's move a lot, it's short and sweet and gets the job done.

Mogulmeister · Joined: 03 May 2007 Posts: 1151

*Nips off to have a look*

tlanglet · Posted: Sun Apr 25, 2010 3:27 pm Post subject:

I was gone for a couple of days and missed this discussion, but I am readily finding "almost" conitions with minimual effort.

For this puzzle, I noticed the UR45 in r69c13 and analyzed the outside row implication to prevent the DP.
Digit 4: r9c46,
Digit 5: r9c4.
The two conditons provide the bases for an AIC: (4)r9c46 = (5)r9c4 - r23c4 = r3c5 - r3c78 = r2c7 - (5=4)r8c7; r8c46<>4.
(Hope I did this one correctly!)