The New Sudoku Players' Forum

[Kit_ISIS_Kat]

I got this from Vol 1, Issue 8 - Mild puzzle # 3 of the Puzzler series "World

Best Sudoku: The Original Handmade Puzzles"

Here is the original puzzle
*-----+-----+--------*
| . . 5 | . . . | 7 . . |
| . 8 . | . 2 . | . 3 . |
| 6 . . | . . 4 | . . 9 |
*-----+------+-----*
| . . . | 6 . . | 5 . . |
| . 3 . | . 9 . | . 4 . |
| . . 4 | . . 5 | . . . |
*-----+------+------*
| 9 . . | 3 . . | 6 . 4 |
| . 1 . | . 8 . | . 2 . |
| . . 7 | . . . | 8 . . |
*-----+-----+-------*

I solved a few numbers and got stuck. I have the Simple Sudoku program with

which I can print the puzzle with or without the "candidate list". It can also

give hints. I got as far as what you see below.

*-------------------------------------------------------------------*
| 1234 249 5 | 189 136 13689 | 7 168 1268 |
| 17 8 19 | 1579 2 1679 | 4 3 156 |
| 6 27 123 | 1578 1357 4 | 12 158 9 |
+-------------------+----------------------+-----------------------+
| 1278 279 129 | 6 4 12378 | 5 1789 12378 |
| 5 3 126 | 1278 9 1278 | 12 4 12678 |
| 1278 2679 4 | 1278 137 5 | 1239 16789 123678 |
+--------------------+----------------------+------------------------+
| 9 25 8 | 3 157 127 | 6 157 4 |
| 34 1 36 | 4579 8 679 | 39 2 357 |
| 234 2456 7 | 12459 156 1269 | 8 159 135 |
*--------------------------------------------------------------------*

When I asked for a hint at this stage, it highlighted R6-C7 with the hint
"Exclude based on naked pairs". No problem - I eliminate the 1 and the 2 but that still left both the 3 and the 9. It wouldn't let me insert the 9 but let
me insert the 3. What I want to know is why the 9 is no good and the 3 is OK.

I looked carefully at R6 and saw that there was at least one other cell with
each of these. Also the mini-grid had more than one cell where the 3 or 9
could go. What have I missed?

[emm]

The hint tells you to remove 12 from r6c7 because of the naked pair in c6. It tells you nothing about the validity of the 3 or the 9 in r6c7.

[Pat]

the Puzzler series World Best Sudoku: The Original Handmade Puzzles
Vol 1, Issue 8
Mild puzzle # 3

Code: Select all

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

tough puzzle - definitely not Mild

here's my guess:
perhaps need add missing clue r3c3=2
(but then it becomes much too easy)

~ Pat

[TKiel]

Multiple colouring on digit 6 leads to the solution. (This is incorrect. It makes some exclusions, but does not solve the puzzle.)

I copied and pasted the puzzle into SS and it didn't indicate that it was asymmetrical. Then I entered Pat's missing clue suggestion and it didn't indicate that puzzle was asymmetrical either. I know there are lots of different kinds of symmetry, but how can both puzzles be symmetrical?

Tracy

[udosuk]

Obviously, both puzzles are symmetrical. The "original" one posted by Kit_ISIS_Kat has diagonally reflective symmetry, while if you add r3c3=2, then it has 180 rotational symmetry too.

I think for the "mild" rating the r3c3 clue has to be given so probably somebody forgot to put it there (a misprint or something)... But if that clue is left out then it transforms to a fiendish monster (but still having a unique solution)... If you get rid of the clue at r7c7 then the puzzle has multiple solutions... So I like it as the way it's now (without the r3c3 clue)...

[Carcul]

Multiple colouring on digit 6 leads to the solution.

I cannot see how. Here is a possible solution (after the X-Wing):

Code: Select all

 *---------------------------------------------------------*
 | 1234  249   5   | 189   136   13689 | 7   168    1268   |
 | 17    8     19  | 1579  2     1679  | 4   3      156    |
 | 6     27    123 | 178   1357  4     | 12  158    9      |
 |-----------------+-------------------+-------------------|
 | 1278  279   129 | 6     4     12378 | 5   1789   12378  |
 | 5     3     126 | 1278  9     1278  | 12  4      12678  |
 | 1278  2679  4   | 1278  137   5     | 39  16789  123678 |
 |-----------------+-------------------+-------------------|
 | 9     25    8   | 3     157   127   | 6   157    4      |
 | 34    1     36  | 4579  8     679   | 39  2      357    |
 | 234   2456  7   | 1249  156   1269  | 8   159    13     |
 *---------------------------------------------------------*


1. [r46c1]-2-[r245c3]-6-[r8c3]-3-[r89c1]-2-[r46c1], => r4c1/r6c1<>2.

2. [r3c3]-1-[r3c7]-2-[r3c2]-7-[r2c1]-1-[r3c3], => r3c3<>1.

3. [r8c4]=5=[r8c9]-5-[r2c9]-6-[r5c9]=6=[r5c3]-6-[r8c3](-3-[r8c7]-9-[r8c4])-3-[r8c1]-4-[r8c4], => r8c4<>4,9.

4. [r8c6]=6=[r8c3]-6-[r5c3]=6=[r5c9]-6-[r2c9]=6=[r2c6]-6-[r8c6], => r1c9/r6c9/r1c6/r9c6<>6.

5. [r4c6]=3=[r4c9]-3-[r9c9]=3=[r9c1]-3-[r8c3]-6-[r5c37]-1,2-[r5c46]-7,8-[r4c6], => r4c6<>7,8.

6. [r4c9]-3-[r6c7]=3=[r8c7]-3-[r8c3]-6-[r5c3]=6=[r5c9]=7=[r5c6]=8=[r1c6]=3=[r4c6]-3-[r4c9], => r4c9<>3.

7. [r2c9]=6=[r5c9]=7=[r5c6]=8=[r1c6]-8-[r1c89]=8=[r3c8]=5=[r2c9], => r5c9<>1,2,8; r5c6/r3c8<>1.

8. [r5c4]-2-[r5c7]=2=[r3c7]=1=[r3c4]-1-[r6c4]-2-[r5c4], => r5c4<>2.

9. [r5c7]-1-[r5c4]-8-[r5c6]-7-[r28c6]-9-[r8c7]=9=[r6c7]{-9-[r46c8]-(UR: r46c18)-7,8-[r6c8]}-9-[r4c8]=9=[r4c2]-9-[r6c2]-6-[r6c8]-1-[r5c7], => r5c7<>1 which solve the puzzle.

Carcul

[gsf]

Obviously, both puzzles are symmetrical. The "original" one posted by Kit_ISIS_Kat has diagonally reflective symmetry, while if you add r3c3=2, then it has 180 rotational symmetry too.

the symmetry without the [33] clue is antidiagonal, with is diagonal+antidiagonal

[TKiel]

I tried to replicate what I did with colouring on 6's and while it does make some exclusions, it does not solve the puzzle. I can only conclude that I made an error somewhere and simply got lucky when whatever cell I assigned as 6 actually turned out to be 6. I'll edit my original post.

Thanks for the answers about the symmetry.

Tracy