A Partial Pattern Trial on ultrahardcore 179

This post starts with the 5-panel freeform  analysis to compare with yours and then moves on with the partial pattern trial suggested in the last post, of 8 patterns containing 8r2c9.

My 5-panel patterns are much less promising  than the 8-panel ones.

Too many patterns in both sets.

On the 8-panel there were two ways to start in the first 2 columns, while the 5-panel has three. Or to put it a better way, on the 8-panel it was 2 clues vs 2 other clues, giving us  2 clues either way. Remember how two clues were enough to get us past solver stalls on UHC 135?

Well we could have decided  that with a lot less work. One thing you get with a full analysis is the orphans, the candidates not on any pattern. Do we have any on the 5-panels?  I think I have one. All 5 pattern freeforms start in r1c9 or r9c9, and none include 5r9c2.  Not much help.

Back to the plan, let’s see if we can get to coloring with two clues from the 8-panel value pattern analysis. It’s one trial to eliminate three or four more. We start by restarting at the stall point with the givens, plus one clue from the bypass, and now with two clues  from one of the 8-pattern sets, 8r2c9 and 8r5c8.

Following up (NE8, E8) with NW5, Beeby pulls in an ALS_75, and we’re off again, but  in trial mode.








Next is an  ANL with an ALS value set on one terminal. The victim must see the whole value set.


Beeby follows with another hat, even more extreme. The 2 value set is crosswise, but there’s still a victim, and it comes with a clue.












We get NE1, and NW1m and W14, which show up here with a hidden UR, type 2.


Next, a couple of Beeby specials, down the middle.

First, a discontinuous 1-way: 5r5c4 is false if 5r3c4 is true, or if it is false, and the slink chain forces it out with a 4 in r5c4. Beeby notes call it a discontinuous loop.Put in the winks, and there is a loop. It’s the alternation of inferences that is discontinuous.









The other special is a complex 1-way.  Complex 1-ways allow slink partners, true when 3r1c6 is false, erase candidates interfere with  the AIC.  You don’t search for these. You just build them with the hope that something will happen. And often enough, it does.


Now a very similar pair of 1-ways, another force out on the left, and a complex ANL on the right.  It’s not a regular ANL, because the chain is 1-way. Two bonus removals are a NWc4 boxline, for a naked pair r2s79, which removes 9r2c4.











Remember, all of this in a trial to see if it’s this or another pair of clues, fits the solution.


Anyway, spot two long ALS in parallel lines with two matching singles and you might have this ALS_64.

In the same neighborhood, a hidden unique rectangle. 3r8c5 would force 2 in two corners, and the slink would force a 3 in the opposite  corner.






The examples keep teaching. Next is an ALS 43 in which both Z sets are not singles, and only one is aligned with the victim. The other one is in the box with it.







Next is a simple AIC ANL whose removal triggers a productive naked pair.




The hidden UR is a direct result, but the removal from a crowded cell is slow progress.



Finally, it happens.  An ANL brings a naked pair in c9, in turn bringing E2. Coloring is on,  and traps leave a single 9 in c4, wrapping green.

The blue army then reaches a contradiction, when it removes the last 9 from W and from c3.





In the breadth first trace below, the blue army then reaches a contradiction,

when it removes the last 9 from W and from c3.


The big picture summary:  We found that the UHC 179 8-patterns allowed only two placements of two 8’s in columns c89. We now know that one of those placements, and all the patterns including it, are false. We can put in the two clues of the other placement, go for a solution next week. And you’re invited.

Could it be time for your next attempt to get there first with the second documented trial free solution of the Stefan Heine ultrahardcore right page Sysudoku review? If you get one, I’ll draw the grids and interpret your moves and guess at how you spotted them for Sysudoku readers, and you can order a box of  copies to hand out to your friends, relatives and other admirers. Here’s the next one, ultrahardcore 223.





About Sudent

I'm John Welch, a retired engineering professor, father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. Sudoku analysis and illustration is a great hobby and a healthy mental challenge.
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