Two Dave Green 4-fills


This post reports Sysudoku Basic on the two Dave Green puzzles of the previous post.

In the Sunday 5-star of 4/17/21 on the left, a 5-fill becomes a 4-fill when N6 drops in.

It is immediately  resolved to a 3-fill as NE4 and SW4 leave one cell for NW4.

When S4 arrives, SE3 does the same for the r8 4-fill, but 7 and 8 can’t decide the remaining cells, until a third 4-fill created by C9 is resolved.

By then, S3 has prepared the way for the resolution.

A fourth 4-fill c2[1257], created by W8,  is left for box marking, even though SW2 claims two cells in c2.

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Of course, 4-fills are created thoughout the bypass.

You can follow every step and make sure, but it looks to me like this Sunday 5-star makes it through box marking and line marking. The many linked bv invite coloring, and a trap on 5r8c7 removes all green candidates for an immediate collapse.

The right side puzzle of 4/18/21 has a resolvable 5-fill, i. e. a line with 5 free cells having an available clue placement. If that isn’t how you started it, scroll back and take a look at c3 of the Dave Green 5-star. Four of the 5 free cells are seen by a 4 clue.  The bypass starts by breaking down this line.

The regular bypass order by value starts from there.

Six more 3-fills along the way, and it’s all bypass.

Starting next week, the weekly posts were scheduled to go on pause, with the 500th post remaining in place with navigation tips and  updated current news on page updates, including The Guide.

However, updates on menu bar pages have gone well, and my update of the KDI 475 made me realize that my earlier report on KrazyDad’s SuperTough collection needed an update.

Anticipating that, you can see the 3-post snapshot version  starting 3/19/2013 on the monthly archive. The pause comes later, if at all.

Comments and requests for new collection reviews are welcome.  Please leave your comments on a relevant post.

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.
This entry was posted in Basic Solving Procedures, Green, Puzzle Reviews and tagged . Bookmark the permalink.

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