Two Colorful Super Grand Masters


Here I continue the review of Sudoku, vol. 3 puzzles with the detailed solving of its SGM 20, and a coloring highlight from SGM 25.

SGM 20 begins like no other puzzle I’ve ever seen of the advanced class, with a center box of three free cells.  So my box marking trace starts with before the numbers.

SGM 20 LM skyscrapersgm 20 LMLine marking ends with a skyscraper. That would ordinarily show up on the 6-panel, but I happened to notice it closing r8.

SGM 20  verificationOn the bv scan, a potential Sue de Coq

NEr2=8(1+7)(2+6)+682

turns out to be very hard to verify.  If (1+7) is missing, two 4’s are forced in r9. What this demonstrates is the value of breadth first tracing. Below is the trace this actually came from.

SGM 20 sdc verfsgm 20 ANL

The verified Sue de Coq makes only one removal, but that triggers the NWr3 boxline.  More decisive is the small ANL from the bv map.  Its

SE1=>SW1=>S9 enables . . .

SGM 20 245 wing

a 245-wing =>    SW5m =>NW5=>(NW7=>(W7, W2),        NWnp24).

sgm 20 coloringThe X-panel now offers nothing but dead fish, but two coloring clusters carry the day. The green and red 4-candidates see each other,  so we have the bridging logic

not(green and red)=> blue or orange

Then we catch a red 7 looking at blue and orange ones, proving orange. This extends the blue green cluster left on r9 and up on c1 to force a second green 4 into r2.  Blue wins!

SGM 25 dbl wrapSuper GM 25 gave up nothing before I got out the crayons, but I was rewarded with a double bridge wrap.  Blue and orange skirmish in the S box, and blue and red skirmish in column 2, so

not(blue and orange) => green and red

and

not(blue and red) =>

green and orange,

which simplifies to

green and (red or orange) = green.  Then green=> S3=>SW3=>SW5=>S5=>red. Its over.

To sum up, I think Sudoku, vol 3. is worth your time.  I hope your copy is put together better than mine was.

Easter MonsterWanna let’s tackle another monster?  Well , in search of human sized monster weapons, I’ve been looking into how a number of experts have tackled the well known and celebrated Easter Monster.  We’ll do a Sysudoku solution of our own. The box marking is pretty easy, since EM essentially gives you nothing.  The line marking is horrid, for the same reason.  Do it, so that if anyone asks, you can say, “Oh, nothing much. I’m just working on the Easter Monster”.

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About Sudent

My real name is John Welch. I'm a happily married, retired professor (computer engineering), timeshare traveling, marathon running father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. The blog is about Sudoku solving. It covers how to start, basic solving to find candidates efficiently, and advanced solving methods in an efficient order of battle. It is about human solving methods, not computer solving.
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