Easy but enjoyable.

Discussion of Andrew's Extreme Str8ts Puzzle, Quarantine Edition #201, May 6 - May 7

pure logic (4*)

An easy one (9 min).

One setti is enough.

singles and 1 x-wing, setti not needed

Basics and one small setti in 11 min

Easy but enjoyable.

Bca/setti 7 enough to solve

Discussion of Andrew's Extreme Str8ts Puzzle, Quarantine Edition #200, May 4 - May 5

Was lucky with the right decision on D7. Didn't follow the alternative contradiction.

bca:7&4&2 sure; 6 possible in col 7 (row D,G,J); I started with 7 impossible in col 7 (-> 6 sure in d) and in row G (-> x8, 6 sure in J, 5 imp. in J) -> solution (I did not proof the alternative)

@jk: I can't follow your argument. I suppose there must be a typo: 7 is a given digit in col 7.
According to my analysis, 7 is a must in all rows and colums (except H / 3 of course), and 6 is possible in rows D, G and J and in col's 6 and 7.

@Mary: Sorry, it's my mistake; correct is: ..I started with 6 impossible in col 7 ..

After CE, D7=28. If D7=2, E3=1, E8=7; no 1 in row G, so 8 in G4 (naked double in col 4), x-wing on 8 DH12, so no 8 left for row F.

@jgrab: The decision in E8 is similar like decision in D7, having the same result.

After decision in D7 and/or E8, as jgrab and Jens wrote above, there is still a lot of work to do: lot of singles, x-wing(s) and finally a 3-fish to solve this enormous beast.

The current zodiac symbol

is.gd/hone567_Taurus

Taurus the Bull is mortally wounded by the Sword of Orion :)

Very nice, thanks! A perfect medium level of difficulty.

Great pattern. Like jgrab, with an UR.

good one

wrong post

Don't post here!

good one

just CE, not even Setti is needed Mr. Setti

Not even your post is needed Mr. Klaus -
Pls. mind my post at the bottom of this page.
Btw: It's no shame, but Settis comments are always the same -

Hi Jens,

maybe not needed but i like it.

i am somewhat paranoid with people who tell me what do do where, always provokes me to do it in a different way.

ride on.

Aye aye, Sir!

I can not see the original comment, but at least 2 users comments here as Setti. So Setti's comments must not be always the same. :)

As of me, I comment rarely, and try not to tell what to do.

Setti, the user, the rule is named after

Hi Setti,

nice to see that you still stick around.

You brought a lot of joy to many people here, including myself. i still remember your post, many years ago, where you first mentioned the reasoning behind your rule, and the breathless silence directly after, and the first response "wow, that is strong". think it was Setti on 8 if i'm not mistaken.

Hi Klaus,

thank you.

I remember also. :) It could be 8, also not sure about it. It was more than 10 years ago, but str8ts is still my favourite variant of sudoku.

Andrew made it possible with many people here who help solving. Glad to have a part to play in it.

Your comment made me happy, thank you again.

Hi Setti,

congratulation to over 10 jears Setti Rule. Your rule is the same time basis of BCA, too. Both helps to come through difficult str8ts.

is.gd/Leren_567_BX2

As usual "the big brother" is a bit harder at the end, yet, the start is even easier than in the first BX puzzle

very nice - no chain

Much harder than BX1 for us, needed a short head chain.

is.gd/Leren_567_BX1

Very nice and easy.

30 min of fun!

Quick and relaxing.

is.gd/Leren_567_B2

Here I needed a short head chain and a UR argument.

Great puzzle. CE, B setti power and patience does ist. No chain needed, instead I used something I'd call a hidden naked pair in a box. Thank you, Leren! BTW: Is ist possible we had this pattern before in one of your early B str8ts?

could you explain b-setti power in more detail?

@Flo: B setti power depends on the following fact:

If a digit is missing from a row/col it must be missing from a box intersecting with that row/col. And vice versa: If a digit is missing from a box it must be missing from a row AND a col intersecting with that box.

Some examples: If a digit x is missing from row A it must be missing from box 1 or box 2 or box 3. If x is missing from A and C ist must be missing from two of the boxes 1,2,3.
Vice versa: If a digit x is missing from box1 it must be missing from A or B or C AND from col 1 or 2 or 3. If x is missing from boxes 1 and 2 it must be missing from two of the rows A,B,C AND once from col 1 or 2 or 3 and once from col 4 or 5 or 6.

In this puzzle (B2) I used B setti power in a more complicated way at one point to prove that 7 in E as follows:
From the beginning it's clear that DF5=67, E46=34 and 6 and 7 have to be in all cols except maybe for col7. So: If 7 not in E then 6 not in E then 6 and 7 are missing from E and col7, but have to be present in all other rows and cols. But then by B setti power 6 and 7 must both be missing from box6 which is not possible. (Note that this argument would not work if 6 and 7 might be missing from more rows and cols.)

Hope that helped.

Ah. this is really a powerful tool. thanks for the detailed explanation!

is.gd/Leren_567_B1

Pretty and pretty easy

same as Tony - fun

Great one, nice and easy

is.gd/Leren_567_X

Chainless fun, but hard work. Exactly the way I like it - thanks again, Leren!

What an amazing beauty! I do agree with Toni: Hard work but solves perfectly step by step. Thank you, Leren!

great puzzle - thanks !!!

Like Toni and pets. Fun!

Discussion of Andrew's Extreme Str8ts Puzzle, Quarantine Edition #199, May 2 - May 3

From absolutely impossible ones to a very simple one - nice for a change, though. 5 mins.

a sweet fast one. many thanks. 8m.

Yes, easy. 6 min.

13' w/c

w/c nice one

9' w/c pure fun

singles singles singles 15min

Discussion of Andrew's Extreme Str8ts Puzzle, Weekly Edition #567, May 2 - May 8

Some X-Wings and BCA 3.

Only CE

I always try to use the Setti rule and the BCA which are based on strictly logical considerations.
In this time at some stage I found that at least one column does not contain 3. So at least one row also does not contain 3. Rows E and G had to be checked because in other rows this number was sure digit. Starting with row G I get a contradiction. Thus row E definitely does not contain 3. This conclusion led to complete solution of the puzzle.