The New Sudoku Players' Forum

[tarek]

Code: Select all

+-------+-------+-------+
| . 7 4 | . . . | 2 5 . |
| 1 . . | 2 8 . | . . . |
| 8 . 5 | . . . | . . . |
+-------+-------+-------+
| . 9 . | . . . | 7 . . |
| . 1 . | . . 2 | . 8 . |
| . . . | . 3 7 | . . 6 |
+-------+-------+-------+
| 3 . . | 5 . . | 6 2 . |
| 2 . . | . 7 . | 5 . . |
| . . . | . . 9 | . . . |
+-------+-------+-------+
.74...25.1..28....8.5.......9....7...1...2.8.....37..63..5..62.2...7.5.......9...


Play this puzzle online

Download Sukaku Explainer

[SteveG48]

Code: Select all

 *-------------------------------------------------------------*
 |   9     7     4     | 136   16    136   | 2     5     8     |
 |   1     3     6     | 2     8     5     | 49    479   479   |
 |   8     2     5     | 7     9     4     | 13    6     13    |
 *---------------------+-------------------+-------------------|
 |dij46    9 cdij38    |e1468  5   eh168   | 7     134   2     |
 |  b46-7  1  abj37    | 469   46    2     | 349   8     5     |
 | dj45    458   2     | 1489  3     7     | 149   149   6     |
 *---------------------+-------------------+-------------------|
 |   3     48    79    | 5    g14   g18    | 6     2     79    |
 |   2     468   189   |f3468  7     368   | 5     1349  1349  |
 |cdj457   456   17    |f346   2     9     | 8     1347  1347  |
 *-------------------------------------------------------------*


7r5c3 = (37)r5c13 - (3|7)r4c3,r9c1 = (456)r469c1&8r4c3 - (6|8=14)r4c46 - 4r89c4 = (41)r7c56 - (1=6|8)r4c6 - 8r4c3&6r4c1 = (37)r45c3|(457)r469c1 => -7 r5c1 ; stte

[Cenoman]

Code: Select all

 +----------------------+--------------------+----------------------+
 |  9       7     4     |  136    16  A136   |  2     5      8      |
 |  1       3     6     |  2      8    5     |  49    479    479    |
 |  8       2     5     |  7      9    4     |  13    6      13     |
 +----------------------+--------------------+----------------------+
 | C46      9     3-8   |  1468   5  Ba168   |  7     134    2      |
 | x467     1     37    |x'469   w46   2     |  349   8      5      |
 | C45   z'C458   2     |y'1489   3    7     |  149   149    6      |
 +----------------------+--------------------+----------------------+
 |  3       48    79    |  5     v14  v18    |  6     2      79     |
 |  2       468   189   |  3468   7   A368   |  5     1349   1349   |
 |  457     456   17    |  346    2    9     |  8     1347   1347   |
 +----------------------+--------------------+----------------------+

Double kraken (8)r478c6 & (6)r5c145, as a net

Code: Select all

(8)r4c6                                              a
 ||
(8-36)r18c6 = r4c6 - (6=458)b4p178                   A, B, C
 ||
(8-14)r7c56 = (4-6)r5c5                              v, w
                 ||
                (6)r5c1 - (6=458)b4p178              x, C
                 ||
                (6-9)r5c4 = (9-8)r6c4 = (8)r6c2      x', y', z'
 =>-8r4c3; ste

[SpAce]

original: Show

Code: Select all

.-------------------------.------------------.--------------------.
|   9       7        4    |  136    16   136 |   2     5     8    |
|   1       3        6    |  2      8    5   |   49    479   479  |
|   8       2        5    |  7      9    4   |   13    6     13   |
:-------------------------+------------------+--------------------:
|  e46      9   abel[3]8  |  1468   5   f168 |   7     14-3  2    |
|  b467     1      a[7]-3 |  469   h46   2   | i(3)49  8     5    |
| ce45+  cek45+8     2    | k1489   3    7   |  j149  j149   6    |
:-------------------------+------------------+--------------------:
|   3       48       79   |  5     h14  g18  |   6     2     79   |
|   2       468      189  |  3468   7    368 |   5     1349  1349 |
|  c45+7  cd45+6     17   |  346    2    9   |   8     1347  1347 |
'-------------------------'------------------'--------------------'

(37)b4p36 = (87)b4p34 - (8|7)r69c12 =UR= (6-5)r9c2 = (5468)b4p8713 - (6|8=1)r4c6 - r7c6 = (14)r75c5 - (4=3@|9)r5c7 - r6c78 = (98)r6c42 - (8=3)r4c3 => -3 r4c8,r5c3; stte

As a net:

Code: Select all

UR(45)r69c12 using internals:


(8)r6c2 - (8=3)r4c3
||
(7)r9c1 - r5c1 = (7)r5c3
||
(6-5)r9c2 = r6c2 -- (5=4)r6c1 - (4=6)r4c1 - (6)r4c6
                 \                          ||
                  - (8)r6c2 = (8)r4c3 ----- (8)r4c6
                                            ||
        (4)r5c7 - r5c5 = (4-1)r7c5 = r7c6 - (1)r4c6
        ||
        (9)r5c7 - r6c78 = (9-8)r6c4 = r6c2 - (8=3)r4c3
        ||
        (3)r5c7

=> -3 r5c3; stte

As a 13x13 TM:

Code: Select all

 7r5c3 7r5c1
 3r4c3       8r4c3
       7r9c1 8r6c2 6r9c2
                   5r9c2 5r6c2
                         5r6c1 4r6c1
                               4r4c1 6r4c1
                         8r6c2             8r4c3
                                     6r4c6 8r4c6 1r4c6
                                                 1r7c6 1r7c5
                                                       4r7c5 4r5c5
 3r5c7                                                       4r5c7 9r5c7
                                                                   9r6c78 9r6c4
             8r6c2                                                        8r6c4
-------------------------------------------------------------------------------
-3r5c3

Code: Select all

.---------------------.------------------.---------------------.
|  9     7       4    |  136    16   136 |   2      5     8    |
|  1     3       6    |  2      8    5   |   49     479   479  |
|  8     2       5    |  7      9    4   |   13     6     13   |
:---------------------+------------------+---------------------:
| b46    9   abi[3]8  |  1468   5   c168 |   7      134   2    |
| b467   1     a[7]-3 |  469   e46   2   | f(3)49   8     5    |
|  45   h458     2    | h1489   3    7   |  g149   g149   6    |
:---------------------+------------------+---------------------:
|  3     48      79   |  5     e14  d18  |   6      2     79   |
|  2     468     189  |  3468   7    368 |   5      1349  1349 |
|  457   456     17   |  346    2    9   |   8      1347  1347 |
'---------------------'------------------'---------------------'

(37)b4p36 = (768)b4p413 - (6|8=1)r4c6 - r7c6 = (14)r75c5 - (4=3@|9)r5c7 - r6c78 = (98)r6c42 - (8=3)r4c3 => -3 r4c8,r5c3; stte

...or to avoid the alternate end point:

(3)r5c7 = [(37)b4p36 = (768)b4p413 - (6|8=1)r4c6 - r7c6 = (14)r75c5 - (4=9)r5c7 - r6c78 = (98)r6c42 - (8=3)r4c3] => -3 r4c8,r5c3; stte

As a double kraken:

Code: Select all

(3)r5c7
||
(9)r5c7 - r6c78 = (9-8)r6c4 = r6c2 - (8=3)r4c3
||
(4)r5c7 - r5c5 = (4-1)r7c5 = r7c6 - (1)r4c6
                                    ||
                                    (6)r4c6 - r4c1 = (6-7)r5c1 = (7)r5c3
                                    ||
                                    (8)r4c6 - (8=3)r4c3

10x10 TM: Show

Code: Select all

 3r4c3 3r5c3
       7r5c3 7r5c1
             6r5c1 6r4c1
 3r4c3                   8r4c3
                   6r4c6 8r4c6 1r4c6
                               1r7c6 1r7c5
                                     4r7c5 4r5c5
 3r5c7                                     4r5c7 9r5c7
                                                 9r6c78 9r6c4
                         8r6c2                          8r6c4
-------------------------------------------------------------
-3r5c3

[SteveG48]

It's interesting that the solutions appear so complicated when the logic is actually quite simple. Take mine:

7r5c3 = (37)r5c13 - (3|7)r4c3,r9c1 = (456)r469c1&8r4c3 - (6|8=14)r4c46 - 4r89c4 = (41)r7c56 - (1=6|8)r4c6 - 8r4c3&6r4c1 = (37)r45c3|(457)r469c1 => -7 r5c1 ; stte[/quote]

I'd actually like to write

7r5c3 = (574)r569c1&3r5c3 - (4|3=68)r4c13 - (6|8=14)r4c46 - (1|4)b8p347 = (14)r7c5 contradiction => r5c3=7, but we just can't accept contradiction.

[SpAce]

Hi Steve,

I'd actually like to write

7r5c3 = (574)r569c1&3r5c3 - (4|3=68)r4c13 - (6|8=14)r4c46 - (1|4)b8p347 = (14)r7c5 contradiction => r5c3=7, but we just can't accept contradiction.

You're right that accepting contradictions would make many solutions simpler. In fact, I don't have anything against it. Go for it, if you feel like it!

That said, I'd find your contradiction chain a bit hard to read quickly for the same (but opposite) reason I don't like normal AICs that start with a weak link. If you start with a strong link I would expect to see a normal AIC (but a contradiction chain or a DNL if you start with a weak link). Thus, I have a couple of suggestions: either 1) start with a weak link and then conclude your initial assumption false, or 2) start with the contradiction (and a strong link) and conclude whatever is in the last link+node (or any direct result of that if clearer).

The latter style is basically the same as yours but reversed. The difference is that it makes the reader quickly aware of the contradiction (instead of surprising them later) and it also makes the conclusion easier to read as it's at the end of the chain. With your style (and option 1) the reader has to go back to the beginning to understand the conclusion, which is an extra step.

I prefer option 2 for the aforementioned reasons, and also because it's an actual AIC (just with a known false node at one end). It works with any DP if you want to write them explicitly. In that style it's also easy to see that the right side of every strong link must be true and the left side false, so one can freely use any right side nodes in the conclusion too. Btw, I picked that style from Dan's really neat solutions which I dubbed "compact krakens". I just modified the entry a little to make it more AIC-like and understandable (at least for me).

Here's how I'd write your logic with both styles (and a third variant):

1) The normal contradiction chain style, starting with the assumption and concluding it false:

(7)r5c1 - (6)r5c1|(73)r43c3 = (68)r4c13 - (6|8=14)r4c64 - (1|4)b8p347 = [!]r7c5 => -7 r5c1; stte

2) A couple of options for the second style:

[!]r7c5 = (1|4)b8p347 - (14=6|8)r4c64 - (68)r4c13 = (6)r5c1|(37)r34c3 => -7 r5c1; stte

DP = (1|4)b8p347 - (14=6|8)r4c64 - (68)r4c13 = (6)r5c1|(37)r34c3 => -7 r5c1; stte

...or to show more explicitly how the last link+node is a direct conclusion by itself:

[!]r7c5 = (1|4)b8p347 - (14=6|8)r4c64 - (68)r4c13 = (6)r5c1|(37)r34c3 - (7)r5c1 => -7 r5c1; stte

[!]r7c5 = (1|4)b8p347 - (14=6|8)r4c64 - (68)r4c13 = (6)r5c1|(37)r34c3 - (7)r5c1 = (7)r5c3 => +7 r5c3; stte

3) An interesting variant without any contradictions (using the known weak link as a generator for the first node):

[(1-4)r7c5] -> (1|4)b8p347 - (14=6|8)r4c64 - (68)r4c13 = (6)r5c1|(37)r34c3 => -7 r5c1; stte

It's interesting that the solutions appear so complicated when the logic is actually quite simple.

Was that also a subtle hint that I could have dropped the unnecessary UR complication along with several nodes and simply start:

(37)b4p36 = (768)b4p413 - (6|8=1)r4c6 ...

? Yeah, I know (now), but I was fixated on the UR

[SteveG48]

It's interesting that the solutions appear so complicated when the logic is actually quite simple.

Was that also a subtle hint that I could have dropped the unnecessary UR complication along with several nodes and simply start:

(37)b4p36 = (768)b4p413 - (6|8=1)r4c6 ...

? Yeah, I know (now), but I was fixated on the UR

Nope. I'm usually not very subtle .

My post was inspired by the fact that all the solutions presented were long, and by my frustration with the fact that my own solution seemed so easy in its essence but was so hard present. Often I see chains that want to end in a contradiction, but then work to twist them around so that the chain goes back over itself in reverse to avoid that.

[SpAce]

Often I see chains that want to end in a contradiction, but then work to twist them around so that the chain goes back over itself in reverse to avoid that.

Yes, I know what you're talking about. I think it's perfectly fine to use a contradiction chain in those cases. It's shorter and clearer than the corresponding (normal) AIC. If it's written using the guidelines I outlined, I would also consider it more elegant in that situation. In fact, I consider this a valid AIC:

[!] = a - b = c => a & c

One or the other end point of an AIC must be true, and since one of them is known to be false (a contradiction, a deadly pattern), the other must be true (along with any other right side nodes). Can't get simpler than that.

Sometimes the truth of 'a' is so self-evident that the preceding false node can be skipped. That's how Dan used to write some of his shortest chains which I called compact krakens. In other words:

[a] - b = c => a & c

It's very neat but a bit harder to understand at first. It probably should be used sparingly, but a very obvious use case is long AICs that are basically mirror images if split in the middle, i.e. what you said above.

[eleven]

Yet another notation for a mix of the solutions by Cenoman and Steve.

Code: Select all

 *----------------------------------------------------------------*
 |  9     7     4     |  136    16   136   |  2     5      8      |
 |  1     3     6     |  2      8    5     |  49    479    479    |
 |  8     2     5     |  7      9    4     |  13    6      13     |
 |--------------------+--------------------+----------------------|
 | A46    9     38    | #1468   5   #168   |  7     134    2      |
 |  467   1     37    |  469    46   2     |  349   8      5      |
 | B45   B458   2     |  1489   3    7     |  149   149    6      |
 |--------------------+--------------------+----------------------|
 |  3     48    79    |  5     b14  a18    |  6     2      79     |
 |  2     468   189   | c3468   7    368   |  5     1349   1349   |
 |  457   456   17    | c346    2    9     |  8     1347   1347   |
 *----------------------------------------------------------------*

(Steve's observation):
1r7c6 = (1-4)r7c5 = 4r89c6 => r4c46 cannot be 14
=> (8=6)r4c46 - (6=4)r4c1 - (4=58)r6c12 => -8r4c3, stte

Or in one line:
1r7c6 = (1-4)r7c5 = 4r89c6 => -14r4c46 => (8=6)r4c46 - (6=4)r4c1 - (4=58)r6c12 => -8r4c3, stte

[SpAce]

1r7c6 = (1-4)r7c5 = 4r89c6 => r4c46 cannot be 14
=> (8=6)r4c46 - (6=4)r4c1 - (4=58)r6c12 => -8r4c3, stte

Too many words and steps. (*) All in one line:

[1r7c6 = (1-4)r7c5 = 4r5c5] - 14r4c64 = [(8=6)r4c46 - (6=4)r4c1 - (4=58)r6c12] => -8 r4c3; stte

or:

[(1-4)r7c5] -> (1|4)b8p347 - 14r4c64 = [(8=6)r4c46 - (6=4)r4c1 - (4=58)r6c12] => -8 r4c3; stte

Both are examples of chains that start with a known fact, the latter being more obvious than the former.

(*) Didn't see that you'd added your own one-liner.

[eleven]

Too many words and steps ...

For you and Steve maybe. Who tells you, that your notation is the one and only, and that you have to "correct" all written by others ?

[SpAce]

Too many words and steps ...

For you and Steve maybe. Who tells you, that your notation is the one and only, and that you have to "correct" all written by others ?

Oh, can't you take it the other way? That's called hypocrisy. I wouldn't have said anything if you hadn't been so eager to criticize my notations (and only my notations) so frequently and aggressively. I've been very patient with that s**t with you, but last time was just a bit too much. I love valid criticism because it helps me learn and improve, but not when it's given in such an arrogant style and without even making much sense. And of course without any concessions, much less apologies, afterwards.

When is the last time you criticized anyone else's notations? I'm very interested in why you seem to have singled out me and mine to face your wrath. Are you really sure they're the worst around here? Since we both know the answer (or if you don't, you have bigger problems), what is the real reason for such blatant double-standards?

Why do you hate me so much? Until the last stupid discussion I'd been mostly very nice to you and frequently expressed appreciation for your solutions etc, including very recently. I regret that now because obviously you've been hating me the whole time. I just didn't know. (Then again, I guess I should have, because it's a pretty good default value with most people around here, lol.)

[eleven]

Stay calm, please.

I don't hate you, I just don't like, that you cannot accept solutions without comment, which are not written in your style.

You may not have understood, but i criticized, that your link was ambiguous, which no others were, i have seen here. No hate.
Yes, i don't like your compressed notations, because it is often hard to understand. But i don't comment them, if i can understand them.

I also criticized, that Denis' oddagon notation does not list the guardians, but i didn't want a discussion about that. (It was neither wrong nor ambiguous.)

[SpAce]

I don't hate you

Probably not. That would imply caring at some level. Blatant disrespect is more like it.

I just don't like, that you cannot accept solutions without comment, which are not written in your style.

First of all, who am I to accept or discard anything, except in my own solutions? I neither have nor think I have such authority over other people. It's totally different personalities who have such narcissistic delusions of grandeur and dreams of absolute power. Mostly I wouldn't even want it because 1) freedom of expression is one of my core values and 2) I believe that a reasonable level of diversity can spawn new ideas and improvements. I've said many times that I wouldn't even want everyone else to write their solutions my way, because I like to get those new ideas, and also because I freely admit that my compact style is not optimal in all regards. Most obviously it's not optimal in all aspects of clarity, but it's a conscious trade-off which I often compensate by providing alternate notations as well.

However, my style (any of them) is certainly pretty optimal in terms of correctness, intrinsic simplicity (*), avoiding clutter, and following (or sometimes establishing) good standards. Even typos are extremely rare. If you disagree, I must seriously question your judgment. Those are attributes that I wouldn't mind seeing in others' solutions too, because they're good traits in any style without any negative trade-offs. That's why I can't always avoid commenting if I see suboptimal notations in those areas, though I guess I just should let them fly like you do. However, they have a direct effect on clarity as well, which you don't seem to acknowledge at all (because you're too busy hating my compressions for that reason).

(*) Added. By 'intrinsic simplicity' I mean that the notation is probably close to minimal in terms of used resources (candidates, digits, cells, etc) for the intended logic. For example, it means that I rather use a small AHS instead of a large ALS and vice versa, unless there's a compelling stylistic reason to do otherwise. The simplifying effects of such choices are often dramatic and easiest to quantify and compare as matrix sizes or even more accurately as the numbers of truths and links. They also have a direct effect on readability. A small AHS is much easier to read than a huge ALS, except for those who've never learned to read AHSs as fluently (but that's their problem, not mine). (Btw, this has nothing to do with compression which is purely a cosmetic trick. It also doesn't imply anything about the complexity of the logic itself.)

Yes, i don't like your compressed notations, because it is often hard to understand.

Yes, they can be that. No disagreement there. Are they really harder to understand than perhaps explicitly but otherwise incorrectly written chains that don't follow any standards and best practices? Based on your past comments and lack of criticism for those kinds of chains, you apparently think so. Sorry if I find that hard to accept. Furthermore, I find your criticism pretty pointless in most cases anyway, because I often provide explicit alternates as well (why not -- those are trivial to write compared to the compressions that take real skill). In that almost-RP case I didn't because it was such a trivial puzzle for which such an unnecessarily complex solution was more or less a joke anyway. I just did it for fun without expecting it to raise such hell. Even then, when you commented I explained my logic thoroughly. You just didn't accept it, but I can't help that.

The fact that, all you apparently see in my chains is that single negative aspect (in just one of the styles I use), is a really simplistic and unfair point of view. In fact, it's probably listed as a logical fallacy, but I can't remember which one (edit: it's actually more likely a cognitive bias). It's inconceivably stupid if you really fail to see that most of my modern notations are virtually perfect in almost any other objectively measurable qualities -- and even that one admitted flaw is mitigated by the alternatives I provide if necessary. If you weren't so biased, for whatever personal reasons (because it obviously can't really be stupidity), you'd see and respect that, no matter how much you hated my compressions. But you don't, or at least you can't admit it, and on my part I can't respect that because it's ignoring obvious facts.

You may not have understood, but i criticized, that your link was ambiguous, which no others were, i have seen here.

There you go again. So, that whole discussion really was a complete waste of time if you still call my link ambiguous. Like I told you several times, I consider ambiguous to mean incorrect. If you want to keep implying that about a chain of mine despite my strongly argued disagreement, you'd better back that up with bullet-proof counterarguments. Otherwise you should clearly state that your definition of "ambiguous" is different from mine, but I don't think even that is a good excuse around here, because I think most would interpret that term the same way I do. I would accept any of "unintuitive" or "inexplicit" or "hard to understand" etc, but not "ambiguous" or "incorrect" unless you prove otherwise.

In fact, I made a mistake with that term in one of my very first discussions with Steve. As you can see, Steve didn't like it very much either, and I understood it very well once I realized my mistake. What I would like to see from you is the same simple concession I made:

I accept that it's not ambiguous

Or otherwise you should provide better arguments for why you stubbornly disagree.

(It's also a fun discussion to read now because it shows how my preferences have shifted over time. It's also why I understand perfectly well why my compact notations aren't necessarily easy to understand. Yet I have my reasons to write them, explained many times elsewhere, and I don't need to apologize for those.)

Yes, i don't like your compressed notations, because it is often hard to understand. But i don't comment them, if i can understand them.

If you don't understand something it doesn't make it ambiguous. That said, I'm extremely surprised that you of all people have trouble understanding even my weirdest and wildest chains. I honestly think that you're one of the smartest players around, mostly based on your exceptionally clever and elegant solutions which I love to see. That's why having these stupid conflicts saddens me. I still have a lot to learn from you, but I also have my limits to how much unfair abuse I'm willing to take for that.