KD Insane 415 Updated

This post tells the story in the solving of Krazy Dad Insane v4, b1, n5, as reported in updated Sysudoku posts of 7/13/13 and 7/20/13. It’s one way that coloring and pattern analysis work together.

Important features of Sysudoku Basic are illustrated on the first screen.  Always included is a complete basic trace in a very compact format. This service is not duplicated elsewhere.

The first grid shows a large number of bypass clues, with very few pencil marks. The 5-wing occurs on the second line marking. How was it spotted? In marking c2, the 5’s are placed at the Southwest corner, marking a line slink.  Form the corresponding habit: when you mark a line slink, look for a parallel one.

Now what happens? No immediate victim, but the fish icons remain and prevent the addition of the pencil marks added, then removed by many other solvers, human and computer.

Next is the line marked grid, where you can see the completed candidate field. If it doesn’t look like yours, then maybe you should look at what else happened to all those pencil marks. And what it means to have the marks placed in the cells as they are. Is this coded information to be used in advanced solving?

Also on the first grid, the first advanced method beyond the 5-wing is in evidence, a blue/green cluster.

The most significant figure of the post, however is this pair of panels. Patterns and coloring come together here. The 5-panel has the  very simple blue/green cluster.  Freeforms are not required to show that the cluster marks two 5 patterns.

Then the 7-panel jumps out at you as being very limited in patterns as well. A quick freeform analysis with r9 as a starting row divides the 7-patterns, three from r9c2 and one from r9c4. Now we mix in a little overlay, some LPO. The 5 and 7 patterns overlay without conflict, except in coloring. There is only one way for slinked 7’s to overlay colors consistently with the 5 coloring. All of the 7-candidates are compatible with all of the 5-candidates. Of course the coloring added to the 5-cluster is limited to the compatible coloring links of the 7-panel.

The benefit of expanding a cluster is to trap candidates and confirm one color. Here is the expanded cluster as the trap sequence begins.

The traps carry KD 415 past the first Sudokuwiki advanced move, but not to a solution.




Instead, three irregular XYZ-wings are found in the growing bv field to continue the blue/green expansion to a wrap of green, and a collapse.

Here is the first of these, a 376-wing where the weak link attaching the 36 wing is a grouped 3-chain. A systematic way to spot these without extensive searching is noted in the bv scan section of The Guide. An important element is the use of an XYZ map to limit consideration to the cell set that can form an XYZ-wing, without regard to cell location. Then for each possible set, you concentrate on building the necessary connecting forcing chains as winks.

The 367 hinge is placed on the map only because the bv 67 and 36 are on it. With the easy wink to wing 76, we are motivated to find a forcing chain to 36 on the grid.

On very difficult puzzles, it would be worthwhile to return to your XYZ map at the AIC building stage, when more types of wing attachments are available.

The second XYZ-wing is a regular XYZ wing, an occurrence more rare than an irregular one. The third XYZ makes up for it. One wing is attached by forcing chain, and the victim sees one toxic set member by forcing chain.

Finally, please be patient with the ads and with the Sysudoku practice of leaving something for readers to try, and backing them up next post. The latter is why the finish of KD 415 was held for the next post.


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Beware 195 Ends a Basic Review

In this final post of the review of Will Shortz’ Hard Sudoku v.1, Beware! Very Challenging 195 is solved in the bypass. The review table is included for comparisons.  A new mode of blog posts will include reports and links to updates on earlier reviews, beginning with the Insane collection from Krazy Dad.

On Beware 195, here is the grid as the fourth 3-fill ted in c6.





Beware 195 is in collapse as 3-fill c6[129] is marked, and we never get back to the previous 3-fill r8[589].

With the modest title, it might have been expected, but Hard Sudoku v.1 measured out to be the easiest of the three Will Shortz collections reviewed here. Three solved in the bypass, and the rest in line marking.

All while assembling candidates for advanced methods.

From one of the easiest to one of the most difficult outside of the monster class, the next posts are about an updated review, originally done in 2013, less than a year after the blog began. The  collection, Krazy Dad Insane stands out in its introduction to human solving refinements now being reported in a consolidated, more accessible form in the Sysudoku Guide.

The next post also marks a departure in the Sysudoku blog.  From 2013 it has been mostly a series of reviews on collections and the views of experts.  The 2012 year was taken up introducing advanced methods, and was written with very few sources of examples.

While such reviews will continue, readers will now be guided to update earlier reviews and navigation pages. The updated posts will remain in the original files by date. Current weekly posts will alert readers to the updates, and comment on them.

Also, where it corrects omissions and creates a more accurate account of Sysudoku methods, results from  Andrew Stuart’s solver, as accessed on sudokuwiki.com, will be reported with acknowledgement.

The 2012 introductions to advanced methods still apply, but are now better accessed in the Guide, where the many refinements are explained in the same pages, and many more examples are cited.

So from now on, you can follow up on posted reports by looking up method explanations in the Guide by subject , and solving history to check your efforts in the original posts by date. Hopefully, most reviews can eventually be updated. Comment with suggestions are welcome.

The KD Insane review posts began with Insane 415 on July 16, 2013. No, there is no 405. The number 415 stands for volume 4, book 1, and number 5.  The review goes through the books in volume 4, picking on number 5 in each book. There is no book 0, but there is a book 10, and a review puzzle 4X5. Please talk me into doing another volume of Insane puzzles.

My advice is to start by going to KrazyDad.com, following links to Sudoku, Insane, v. 4 and trying book 1, number 5 yourself, just to get in the swing. The puzzles are free, but Krazy Jim wouldn’t mind a donation eventually.

Then go to the original post. If you haven’t tried it, use the monthly archive list to the right. On the page, you’ll see why each post begins with a brief summary. Click on The Insane Review Begins, and maybe bookmark that until you finish with the post. Read some, and you’re ready for the next post, which will comment on the updated solution.

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Beware 185 Finished in Line Marking

A basic clinic is concluding  for those wishing to make assembling candidates an entertaining task. It is Sysudoku basic on Will Shortz’ Hard Sudoku v.1.  The solution detailed this week is Beware! Very Challenging 185.

Here is the basic trace to within a few obvious moves of the solution.

The bypass grid shows what clues and closed subsets of candidates can be identified before any other candidates are sought.







The box marked grid shows the strongly linked pairs of candidates, the ones most affecting  the placement of clues and other candidates.

Beware 185 is solved after five lines are marked. The challenge for all of these puzzles is in the bypass.



Beyond that, there’s nothing hard about Hard Sudoku v.1.

The solution of one last Hard Sudoku review puzzle, Beware 195, will be traced out next week. Try for a bypass solution.

The next post also begins a series of posts reporting on update results on earlier reviews. It is time to apply seven years of Sudoku experience to the whole blog. The series begins with KrazyDad Insane collection. Six of the review puzzles have now been updated, the entire series running from 7/16/2013 to 9/10/2012. It’s easy to pull them up with the monthly archive list to your right.


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Beware 175 Follows Suit

This continues the review of Will Shortz’ Hard Sudoku v.1, with another documented basic finish. Starting the Guide?  Accounting for each move in this series, then trying them beforehand, will make Sysudoku basic yours.

Beware 175 matches 165’s collapse point, but with slightly different triggers, a boxline and a naked pair.








The box/line interaction, or boxline, occurs when marking line r5. No 9 candidate appears in r5 outside the East box, so the true 9 is in r5. The other E9 hopefuls must clean out their desks, and leave the building.





The naked pair begins the collapse.










Next week, its Beware 185.  The Hard Sudoku v.1 review ends with 195, then my plan is return to earlier reviews to update all review posts to Guide methods and drawing conventions, with weekly post reporting on changes. The earlier posts will remain accessible through Title and Find It pages, and the monthly archive pages. New collection reviews can be undertaken on reader request.

The first review update is half done. It is the KrazyDad Insane collection, beginning mid July 1013.

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A Hidden Single Dispatches Beware 165

This post continues a review of Will Shortz’ Hard Sudoku, v.1. with the sixth of ten pre-selected puzzles. Each one is resolved at the basic level. The detailed review requires time and patience,   but its value is the detailed examples of Sysudoku Basic, an entertaining and efficient way to prepare the grid for advanced  methods. The starting point for reading this blog is the Guide, a network of pages accessed from the menu bar above.

A tough line marking of Will Shortz’ Hard Sudoku v.1 Beware 16 ends with a hidden single.










Here’s the grid at the hidden single SWhs4. In row 7, with six cells unclaimed, only one is available for 4.







Next is Beware! Very Challenging 175.

You also might enjoy following the update posts reviewing Krazy Dad’s Insane collection, beginning in July 16, 2013. It’s the beginning of an effort to update earlier post examples based on what I think I’ve learned since.

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Be Especially Aware 155

This post demonstrates how, in line marking, the partially line marked grid invites the error of using  an incompletely marked cell as a completely marked one.

Every Beware in this review of Will Shortz’ Hard Sudoku v.1 highlights a different basic challenge. This illustrates why treating the basic stage seriously is a source of enjoyment not to be missed.

In Beware 155 most placements occur on a grid with five marked and four unmarked lines in each direction. Here is the grid as a long collapse begins with a hidden single N7 in c6.

In conventional basic, we would finish the line marking before seeking clues.


But its Sysudoku Basic, which continues from N5 as reported in this basic trace.

Now let’s examine the grid where the c6 naked pair 69 confirms N8.  It does because c6 is line marked and we know the entire contents of r3c6.  Looking over at r3c1, we might think we have a clue 8r2c2. But we don’t, because c1 is not marked, and we don’t know there is not an 8 candidate in r2c1.


We are not digital computers.  Such a mistake is based on the type of assumption our brain makes every waking moment, just to navigate our clamorous world. The fill strings along the edges are a record of what is line marked and what is not. As we line mark, we must stay aware of the fill string record.

Moving down the trace a little further, we reach the point where the contents of r3c5 is settled, and the hidden single C8 can be declared.

But we trace it as c5hs8 because column 5 is the unit in which the value 8 has only one place.

Beware 155 is solved without marking another line via fill string.

Next  comes Beware! Very Challenging 165 in the Will Shortz Hard Sudoku v1 review.  Yes, another challenge of your line marking concentration. Or, if you’re a skeptic, try it your way and compare, with data.

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It’s the Bypass In Hard Sudoku v1 145

I had Will Shortz’Hard Sudoku v.1 145 collapsing in box marking, showing that every phase of Sysudoku Basic is actively solving, not just accumulating candidates for advanced methods later. But in process of writing this up, I discovered that the bypass had found a way to keep its collapse going.

Here is the basic trace.

I had missed that the chute 3-fill Cr4[158] leaves the c4 naked pair 69, that also completes the r8 naked pair 69, that gives SW8 and two more clues in the SW box.

It works, because subset pencil marks are posted in the slink marking bypass.



Next,  the review continues with Hard Sudoku v1  155.

On the advanced front, the review of KrazyDad’s Insane collection is being updated, for pattern analysis examples in the Guide. So far updates of July 2013 on Insane 415 and 425 are posted.

The AIC Hinges page of the Guide is being revised to include the AIC boomerang, a type of elimination ANL with its own spotting technique.

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