The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |..7|.9.|1..|
 |.9.|2.8|.6.|
 |3..|.6.|..9|
 |---+---+---|
 |.1.|...|.8.|
 |7.6|...|5.1|
 |.3.|...|.7.|
 |---+---+---|
 |2..|.4.|..5|
 |.4.|7.5|.1.|
 |..8|.2.|4..|
 *-----------*


Play/Print this puzzle online

[Leren]

Code: Select all

*-----------------------------------------------------------------------*
|e4568   2568   7       | 345    9      34      | 1      245   d248     |
| 145    9      145     | 2      157    8       | 37     6      347     |
| 3      258    1245    | 145    6      147     | 278    245    9       |
|-----------------------+-----------------------+-----------------------|
| 459    1      2459    | 456    57     2467    | 2369   8      2346    |
| 7      2-8    6       | 3489  a38     2349    | 5      24     1       |
|f4589   3      2459    | 1456-8 15     1246    | 269    7      246     |
|-----------------------+-----------------------+-----------------------|
| 2      67     13      | 13689  4      1369    | 678    39     5       |
| 69     4      39      | 7     b38     5       | 268    1     c268     |
| 156    567    8       | 1369   2      1369    | 4      39     67      |
*-----------------------------------------------------------------------*

(8=3) r5c5 - (3=8) r8c5 - r8c9 = r1c9 - r1c1 = (8) r6c1 => - 8 r5c2, r6c4; stte

Leren

[StrmCkr]

Code: Select all

.------------------.------------------.-----------------.
| 4568  2568  7    | 345    9    34   | 1     245  248  |
| 145   9     145  | 2      157  8    | 37    6    347  |
| 3     258   1245 | 145    6    147  | 278   245  9    |
:------------------+------------------+-----------------:
| 459   1     2459 | 456    57   2467 | 2369  8    2346 |
| 7     28    6    | 3489   38   2349 | 5     24   1    |
| 4589  3     2459 | 14568  15   1246 | 269   7    246  |
:------------------+------------------+-----------------:
| 2     67    13   | 13689  4    1369 | 678   39   5    |
| 69    4     39   | 7      38   5    | 268   1    268  |
| 156   567   8    | 1369   2    1369 | 4     39   67   |
'------------------'------------------'-----------------'

Finned Swordfish: 8 r357 c247 fr5c5 => r6c4<>8; stte

this move is valid right from the start before applying any locked sets/subset techniques. {but it won't render those moves obsolete}

[Cenoman]

Code: Select all

 +----------------------+----------------------+---------------------+
 | 456-8  2568   7      | 345     9     34     | 1      245   248    |
 | 145    9      145    | 2       157   8      | 37     6     347    |
 | 3     a258    1245   | 145     6     147    |b278    245   9      |
 +----------------------+----------------------+---------------------+
 | 459    1      2459   | 456     57    2467   | 2369   8     2346   |
 | 7      2-8    6      | 3489    38    2349   | 5      24    1      |
 |f4589   3      2459   |e14568   15    1246   | 269    7     246    |
 +----------------------+----------------------+---------------------+
 | 2      67     13     |d13689   4     1369   |c678    39    5      |
 | 69     4      39     | 7       38    5      | 268    1     268    |
 | 156    567    8      | 1369    2     1369   | 4      39    67     |
 +----------------------+----------------------+---------------------+

SF (8)r3c2 = r3c7 - r7c7 = r7c4 - r6c4 = r6c1 => -8 r1c1, r5c2; stte

Cenoman

[eleven]

New hobby:

Code: Select all

 *----------------------------------------------------------*
 | 4568  2568  7     | 345    9    34    | 1     245 e248   |
 | 145   9     145   | 2      157  8     | 37    6    347   |
 | 3    c258   1245  | 145    6    147   |d278   245  9     |
 |-------------------+-------------------+------------------|
 | 459   1     2459  | 456    57   2467  | 2369  8    2346  |
 | 7    b28    6     | 3489  b38   2349  | 5     24   1     |
 | 4589  3     2459  | 14568  15   1246  | 269   7    246   |
 |-------------------+-------------------+------------------|
 | 2    b67    13    | 13689  4    1369  | 678   39   5     |
 |b69    4    b39    | 7     a38   5     | 268   1    268   |
 | 156  b567   8     | 1369   2    1369  | 4     39   67    |
 *----------------------------------------------------------*

(8=3)r8c5-(3=25)r5c25,b7p2468-(2|5=8)r3c2-r3c7=r1c9 => -8r8c9

[JC Van Hay]

OT? Side note :

As a general rule and to complete Keith's principle :
1. If the puzzle contains only 3 solved cells on a principal or not diagonal for a single digit d,
2. If the unsolved boxes doesn't contain locked candidates for the digit d,
3. Just look if there is an X-Chain, i.e. Swordfish (unfinned, finned or Sashimi), in the column or in the row.

Extended Keith's principle : there is no [NxM!]fish on the digit d if there is no rectangle of boxes or no six boxes outside a "diagonal" for the unsolved, but not locked, digit d.

Empirical rule :
If a puzzle doesn't have a fish for more than 4 digits, then it is [generally] easy (SER<8.2).

Application to the puzzle :
1. No single, no fish only for the 7 while filling the grid with candidates for each digit.
2. There is only one fish on the 8s.
3. Subsets and locked candidates imply no fish for the digits 3 and 9, but the puzzle is already solved if the fish(8) is done first!
4. This puzzle is interesting as it breaks the empirical rule! This not the only not too often case as there exists also "difficult" puzzles, eventually solved by fish(es), where there are only fishes on 4 unsolved digits.

Lesson :
Looking for singles, locked candidates and fishes, before all the subsets, is the easiest thing to do, at least, if not only, for a manual solver. That's why fishes should belong to basics like in a latin square !

[eleven]

Personally i don't look for bigger fish, when solving manually, just strong links (x-chains).

Who likes fish should look at blues' puzzle here (20-clue).

[JC Van Hay]

Thanks, eleven.

Interesting puzzle. Here is my analysis (Hope not too many typos) :

Code: Select all

7 . .|3 . 9|. . 4
. 8 .|. 6 .|. 5 .
. . .|. . .|. . .
-----+-----+-----
4 . .|. . .|. . 5
. 5 .|. . .|. 1 .
9 . .|. . .|. . 3
-----+-----+-----
. . .|. . .|. . .
. 2 .|. 8 .|. 6 .
3 . .|5 . 4|. . 9


0 Single
Only 1 solved cell for the digits 127!
Filling the grid with the bilocals and locked candidates
No fish on 5
Pointing{6B8} -> -{6r7c123}
Pointing{8B2} -> -{8r3c789}
[Jellyfish{2C1469 or 2R1469} -> -{2r5c5}]
[Swordfish{3C258 or 3R258} -> -{3r4c6}]
[Swordfish{4C258 or 4R258} -> -{4r6c4}]
[XWing{6C19} -> -{6r2c237, 6r5c3467}]
[XWing{8C19} -> -{8r5c3467, r7c378}]
Swordfish{9C258 or 9R258} -> -{3r4c4}
HP(39)r2c37, 4r2c4=4
HP(49)r37c2, 3r4c2=3

Analysis of the solved cells in each unit
Solved Cells (349)R1.C1 -> HT(349-1256)r2c3.r3c23
Solved Cells (345)R9.C9 -> HT(345-1278)r7c78.r8c7

Determination of the type of clusters [1 or V or Y] of X-bilocals
Determination of the length of the X-chains
Loop : XWings{(68)C19} -> -{6r3c7, 6r5c3467, 8r5c3467, 8r7c3}, HP(68)r5c19
Pointing{2B4} -> -{2r1c3}; Swordfish{2R1C9R9} -> -{2r3c78, 2r34567c5}
Swordfish{7R2B9C2} -> -{7L6C6}

no Fish on 345

Suggested by the initial SFs(349) :
Purple Cow{4C85, 3C5} -> -3r7c8; 21 singles

No Fish on the solved digits 3459

Analysis of the 7s from 7R5, for example, shows there is only 1 solution initiated by 7r8c9.
Interpretation :
Remotely Finned Jellyfish{7R2357} -> -{7r48c6}; stte

Shorter path :
The Purple Cow appears after the first 2 HP. Therefore :
1. HP(39)r2c37, 4r2c4=4; HP(49)r37c2, 3r4c2=3
2. Purple Cow{4C85, 3C5} -> -3r7c8; 3 singles
3. HP(39)r57c5; 17 singles
4. Remotely Finned Jellyfish{7R2357} -> -{7r48c6}; stte

[StrmCkr]

Purple Cow

oh that brings back
Memories