dailysudoku.com

Tks to both of you! I learned a lot from your help.
By the way, what does the "boomer" mean here? new comer or green hand?
P.S.: I am in China.

Hi, cavalier!

The term 'boomer' is short for 'baby ...

...which can be spotted (without candidates/pencilmarks), because you have 2 and 6 both in column 3 and in row 7.
Thanks for that insight, ravel - very helpful & motivating!

Some of us aging boom ...

It takes two steps. Consider the candidate list at this point: *--------------------------------------------------------------------*
| 5 89 138 | 7 #1369 1368 | 36 4 2 ...

After reaching MJ's first position I found that hypothesizing r1c1=1 forces a contradiction:

?r1c1=1 -> r4c2=6 -> ( r4c46={78}, r5c4=6 ) -> r56c5={39}
?r1c1=1 -> r9c1=8 -> r9c9=9 -> ...

Chuck, i ALMOST got your explanation but am so confused that i can't figure out what you mean by the R19C37 rectangle in this puzzle.

Would youplease illustrate this?
Mimi

My apologies, Mimi! Gues ...

*-----------------------------------------------------------------------------*
| 1 2456 2467 | 379 3489 348 | 345678 347 4568 |
| 47 3 9 | 6 5 ...

*--------------------------------------------------------------------*
| 3 7 9 | 8 46 146 | 5 16 2 |
| 45 2 45 | 169 469 7 | 16 ...

No, I am not so sure or do not understand the X-wing technic so well.
There is still a possibility for a "7" in r9c8

Here's the candidate list after the 16 moves: *----------------------------------- ...

Bill,

If your 16 moves correspond to the hints, there is an X-Wing in '7' at R19C37. This eliminates 7 as a candidate from R1C4, leaving 9 as the only possibility.

HTH,
Chuck

As to symmetry, asymmetry is the exception, not the rule, but as far as I know, it doesn't impact the techniques that generate all the spirited discussion. I guess nobody took issue because nobody car ...

Hi, Marty!

My comments weren't meant for anyone specifically, but more to indicate reasons behind my preference, in case anyone was honestly curious. I did try to respond to humor with humor, and wou ...

Well, I was gonna button my lip but I found another $.02 in my pocket...

Some people find snails disgusting; others consider them a delicacy. "De gustibus...", as I noted earlier. Why begrudge someon ...

Anyway, I cannot understand the issue of not wanting to assume uniqueness, among people who do not want to solve non-unique puzzles.

De gustibus non est disputandum, I guess; I don't understand why s ...

I just prefer not to assume something that can be proved or disproved.

Is there anything else?

Yes.
http://en.wikipedia.org/wiki/Entscheidungsproblem
http://en.wikipedia.org/wiki/G%C3%B6del%27s_inco ...

What's up with this business of not assuming uniqueness? You already know the puzzle has a unique solution, so why assume otherwise? Is this just another way of saying that you prefer to solve puzzles ...

Thanks for the additional info, David, and especially for that rabbit hole on "uniquity". 'Iniquity' came to my mind, too. Scary! Laughing

I''m also beginning to recognize you 'old hands' and deep ...

Many thanks, ravel!

The ALS reference was an interesting read, too.

Cheers!
Chuck

This was interesting!! I'm a little quirky, I guess, but I generally prefer not to assume a priori that a puzzle has a unique solution. If it does, that'll come out in the wash. Consequently, I don't ...

Interesting discussion!

Like Marty, I've been doing this for a little while and also go to forcing chains when necessary. (in my case, when the hints run out! Wink

)

This technique is akin to 'proof ...

And I retract my congrats for discovering how to do it in the grid and extend it for having the patience to enter it manually so it looks as good as a grid. :D

Ah, the logic of a genuine Sudoku addi ...