The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |1..|...|8..|
 |823|.9.|..7|
 |...|.84|3..|
 |---+---+---|
 |6..|.5.|...|
 |2.8|36.|.9.|
 |...|...|68.|
 |---+---+---|
 |97.|.1.|...|
 |..6|.4.|17.|
 |...|..6|95.|
 *-----------*


Play/Print this puzzle online

[SteveG48]

Code: Select all

 *-----------------------------------------------------------------------------*
 | 1       4569    4579    | 2567    237     2357    | 8       26      2569    |
 | 8       2       3       | 156     9      a15      |b45      146     7       |
 | 57      569     579     | 12567   8       4       | 3       126     12569   |
 *-------------------------+-------------------------+-------------------------|
 | 6       1349    1479    | 124789  5       1289-7  |b247     1234    1234    |
 | 2       145     8       | 3       6      a17      | 45-7    9       145     |
 | 3457    13459   14579   | 12479   27      1279    | 6       8       12345   |
 *-------------------------+-------------------------+-------------------------|
 | 9       7       245     | 258     1       2358    |b24      2346    23468   |
 | 35      358     6       | 2589    4       23589   | 1       7       238     |
 | 34      1348    124     | 278     237     6       | 9       5       2348    |
 *-----------------------------------------------------------------------------*


(7=15)r25c6 - (5=247)r247c7 => -7 r4c6,r5c7 ; stte

[SpAce]

Code: Select all

.--------------------.----------------------.---------------------.
| 1     4569   4579  | 2567    237    2357  |  8      26    2569  |
| 8     2      3     | 156     9    a[15]   | a4[5]   146   7     |
| 57    569    579   | 12567   8      4     |  3      126   12569 |
:--------------------+----------------------+---------------------:
| 6     1349   1479  | 124789  5      12789 |  247    1234  1234  |
| 2     145    8     | 3       6    b(7)-1  | b4(57)  9     145   |
| 3457  13459  14579 | 12479   27     1279  |  6      8     12345 |
:--------------------+----------------------+---------------------:
| 9     7      245   | 258     1      2358  |  24     2346  23468 |
| 35    358    6     | 2589    4      23589 |  1      7     238   |
| 34    1348   124   | 278     237    6     |  9      5     2348  |
'--------------------'----------------------'---------------------'

H2-Wing:

(15)r2c67 = (57)r5c76 => -1 r5c6; stte

[SCLT]

Code: Select all

+----------------------+----------------------+--------------------+
|  1     4569   4579   |  2567    237  2357   |  8    26    2569   |
|  8     2      3      |  156     9   c15     | d45   146   7      |
|  57    569    579    |  12567   8    4      |  3    126   12569  |
+----------------------+----------------------+--------------------+
|  6     1349   1479   |  124789  5    12789  | a47-2 1234  1234   |
|  2     145    8      |  3       6   c17     | b457  9     145    |
|  3457  13459  14579  |  12479   27   1279   |  6    8     12345  |
+----------------------+----------------------+--------------------+
|  9     7      245    |  258     1    2358   | d24  2346  23468   |
|  35    358    6      |  2589    4    23589  |  1    7     238    |
|  34    1348   124    |  278     237  6      |  9    5     2348   |
+----------------------+----------------------+--------------------+


Couldn't find anything very different, here's an alternative view of roughly the same logic:

7r4c7 = r5c7 - (7=15)r25c6 - (5=42)r27c7 => -2r7c7 ; stte

[SpAce]

Couldn't find anything very different, here's an alternative view of roughly the same logic:

Quite often these puzzles have just one obvious weakness so the easiest solutions pretty much have to be built around it, one way or another. Such alternative views are still valuable because they show that the same thing can be seen in many different ways.

However, if you want to try something different (and more challenging) with this one, the 4r2c7 is a bit more interesting target. Not very hard, but not trivial either. (Obviously it doesn't make much practical sense, but it's a good exercise.)

Added. Since there were no takers, here's how I'd do it:

Code: Select all

.-----------------------.--------------------.------------------------.
|  1     e4569   d4579  | 2567    237  2357  |   8     26      2569   |
|  8      2       3     | 156     9    15    |   5-4   146     7      |
|  57     569     579   | 12567   8    4     |   3     126     12569  |
:-----------------------+--------------------+------------------------:
|  6      1349    1479  | 124789  5    12789 |   27-4  1234    1234   |
|  2     f145     8     | 3       6    17    | g(4)57  9      f145    |
|  3457   13459   14579 | 12479   27   1279  |   6     8       12345  |
:-----------------------+--------------------+------------------------:
|  9      7      c2(4)5 | 258     1    2358  | a[4]2   36-24   368-24 |
| b35    b358     6     | 2589    4    23589 |   1     7      b238    |
| d34    d1348   d124   | 278     237  6     |   9     5      e2348   |
'-----------------------'--------------------'------------------------'


(4=2*)r7c7 - (2=385)r8c912 - (*2|5=4)r7c3 - r1c3|r9c123 = r1c2&r9c9 - r5c29 = (4)r5c7 - loop => -4 r24c7,r7c89; -2 r7c89; stte

Derived SIS:

(4)r7c7 == (4)r7c3&r1c2&r9c9&r5c7
(2)r7c7 == (2)r7c3 == (2)r8c9

Code: Select all

             -------------- (2)r7c3    (4)r1c3 = r1c2 --- (4)r5c2
           /                ||        /                   ||
loop - (4=2)r7c7            (4)r7c3 -                     (4)r5c7 - loop
           \                ||        \                   ||
            (2=385)r8c912 - (5)r7c3    (4)r9c123 = r9c9 - (4)r5c9


7x7 TM: Show

Code: Select all

 4r7c7   2r7c7
         2r8c9  3|8r8c9
                38r8c12 5r8c12
         2r7c3          5r7c3  4r7c3
                               4r1c3   4r1c2
                               4r9c123       4r9c9
 4r5c7                                 4r5c2 4r5c9
--------------------------------------------------
-4r24c7 -2r7c89


[rjamil]

Code: Select all

1.....8..823.9...7....843..6...5....2.836..9.......68.97..1......6.4.17......695.
 +--------------------+--------------------+--------------------+
 | 1     4569   4579  | 2567    237  2357  | 8      26    2569  |
 | 8     2      3     | 156     9    (15)  | (45)   146   7     |
 | 57    569    579   | 12567   8    4     | 3      126   12569 |
 +--------------------+--------------------+--------------------+
 | 6     1349   1479  | 124789  5    12789 | 27-4   1234  1234  |
 | 2     145    8     | 3       6    (17)  | (457)  9     145   |
 | 3457  13459  14579 | 12479   27   1279  | 6      8     12345 |
 +--------------------+--------------------+--------------------+
 | 9     7      245   | 258     1    2358  | 2-4    2346  23468 |
 | 35    358    6     | 2589    4    23589 | 1      7     238   |
 | 34    1348   124   | 278     237  6     | 9      5     2348  |
 +--------------------+--------------------+--------------------+

Almost Locked Set: 1457 @ r25c67 => -4 @ r47c7; stte

R. Jamil

[SpAce]

Hi rjamil,

Almost Locked Set: 1457 @ r25c67 => -4 @ r47c7; stte

Those are valid eliminations using those cells and candidates, but your description of the move doesn't mean anything. "Almost Locked Set" (ALS) is not a move; it's a pattern that can't accomplish anything on its own (just like any other almost-pattern). It's always used in combination with others or a chain (well, it's a chain either way). Your move contains three connected ALSs, which makes it an ALS-XY-Wing move (an overlapping one, actually). It's best described as an AIC:

(4=5)r2c7 - (5=17)r25c6 - (7=54)r25c7 => -4 r47c7; stte

The three cooperating ALSs are the almost-naked-single (45)r2c7 and the two almost-naked-pairs (157)r25c6 and (457)r25c7. The r2c7 is part of two overlapping ALSs, which makes this a bit different from a normal ALS-XY-Wing, though it works exactly the same way. The chain guarantees that one or the other ALS at the two ends actually locks (i.e. it's no longer almost), so either you have a naked single 4r2c7 or a naked pair 45r25c7. That lets you eliminate anything they both see (the other 4s in c7).

[rjamil]

Hi SpAce,

Those are valid eliminations using those cells and candidates, but your description of the move doesn't mean anything. "Almost Locked Set" (ALS) is not a move; it's a pattern that can't accomplish anything on its own (just like any other almost-pattern). It's always used in combination with others or a chain (well, it's a chain either way). Your move contains three connected ALSs, which makes it an ALS-XY-Wing move (an overlapping one, actually).

I have a difficulty in distinguishing various types of ALSs. I stopped coding them into my solver after just first one pattern completed.

Well, I recognized them as WXYZ-Wing move earlier. Am still theoretically generating various patterns of ALS that contain 4-cells having exactly 4-clues in total without knowing/mentioning separate move name.

With my little knowledge, I will consider 4-cells having exactly 4-clues, not covered as either WXYZ-Wing or XY-Ring moves, as generic "Almost Locked Set" move at the moment.

R. Jamil

[SpAce]

I have a difficulty in distinguishing various types of ALSs.

I still think you're talking about various types of ALS moves instead of ALSs themselves. That is the important distinction you should at least make.

With my little knowledge, I will consider 4-cells having exactly 4-clues, not covered as either WXYZ-Wing or XY-Ring moves, as generic "Almost Locked Set" move at the moment.

I suggest you use a generic term like "ALS move" (or something similar) if you can't tell the exact type (ALS-XZ, ALS-XY-Wing, etc). Calling them just "Almost Locked Sets" is incorrect and confusing, because the full multi-house pattern is not an ALS.

FYI, an "Almost Locked Set" (ALS) is just N cells with N+1 digits within exactly one house. (Similarly, an "Almost Almost Locked Set" (AALS) is N cells with N+2 digits within one house, and so on.) Like I said, they do nothing by themselves, but only when combined into a chain. The resulting combo is not an "Almost Locked Set". No pattern that occupies more than one house is. That should be an easy rule to remember.

[rjamil]

Hi SpAce,

I suggest you use a generic term like "ALS move" (or something similar) if you can't tell the exact type (ALS-XZ, ALS-XY-Wing, etc).

Many thanks for suggesting to use workaround generic term "Almost Locked Set move" instead of specific move name.

I am collecting various patterns of 4-cells having exactly 4-clues in total. hope to restart thinking and try to optimize for speed searching (bulk puzzles).

R. Jamil

[SpAce]

Many thanks for suggesting to use workaround generic term "Almost Locked Set move" instead of specific move name.

No problem. Glad if it helped. One more thing:

I am collecting various patterns of 4-cells having exactly 4-clues in total.

You mean digits. Clues are the same as givens, i.e. numbers present at the start of the puzzle.

[rjamil]

Hi SpAce,

You mean digits. Clues are the same as givens, i.e. numbers present at the start of the puzzle.

Ok. I will change my wordings for candidate as "clues" and will use word "values" instead in future.

R. Jamil