The New Sudoku Players' Forum

[smurfdaddy]

I have been doing S for about 6 months. I guess I understand some advanced techniques but get lost when I read Angus explaining x wings and swordfish. Can't solve this with my skill level. Any tip would be great (I'm probably missing an obvious double or something. Sorry about the sloppy chart.

3 248 128 48 124 9 6 7 5
1247 5 1278 6 124 28 9 3 128
6 289 1289 5 7 3 12 18 4


1257 2378 12578 9 68 4 12357 156 1237
47 3479 6 2 5 1 8 49 379
1245 2489 12589 3 68 7 1245 14569 129


8 27 257 147 9 6 13457 145 137
79 6 4 178 3 5 17 2 89
579 1 3 478 24 28 457 89 6 [/list]

[keith]

You are not missing any obvious basic move, or even one of the most popular "advanced" moves. This needs a chain.

Code: Select all

+-------------------+-------------------+-------------------+
| 3     248   128   | 48    124   9     | 6     7     5     |
| 1247  5     1278  | 6     124   28a   | 9     3     128c  |
| 6     289   1289  | 5     7     3     | 12    18    4     |
+-------------------+-------------------+-------------------+
| 1257  2378  12578 | 9     68    4     | 12357 156   1237  |
| 47    3479  6     | 2     5     1     | 8     49    379   |
| 1245  2489  12589 | 3     68    7     | 1245  14569 129   |
+-------------------+-------------------+-------------------+
| 8     27    257   | 147   9     6     | 13457 145   137   |
| 79    6     4     | 178   3     5     | 17    2     89d   |
| 579   1     3     | 478   24    28b   | 457   89e   6     |
+-------------------+-------------------+-------------------+


There is a solution via "strong links" or "multi-coloring". Look at C6 and C9. They each contain only two candidates for <8>.

One or both of the cells labeled "b" and "d" must be <8>. Think about it! (If neither of them is <8>, both "a" and "c" must be <8>, a contradiction.)

So, R9C8 ("e") cannot be <8>, it must be <9>, and this solves the puzzle.

This pattern is sometimes called a "fork". It is two strong links that almost form an X-wing.

Best wishes,

Keith

[Crazy Girl]

smurfdaddy,

to summarise here is where you are stuck.

Code: Select all

----------------+-------------+------------------|
3    248  128   | 48  124 9   | 6     7     5    |
1247 5    1278  | 6   124 28* | 9     3     128A |
6    289  1289  | 5   7   3   | 12    18B   4    |
----------------+-------------+------------------|
1257 2378 12578 | 9  68   4   | 12357 156   1237 |
47   3479 6     | 2   5   1   | 8     49    379  |
1245 2489 12589 | 3  68   7   | 1245  14569 129  |
----------------+-------------+------------------|
8    27   257   | 147 9   6   | 13457 145   137  |
79   6    4     | 178 3   5   | 17    2     89B  |
579  1    3     | 478 24  28* | 457   89A   6    |
----------------+-------------+------------------|

looking at the 8's...there is only two cells in the same two columns in block 3 and in block 9 that contain 8, so applying colouring starting at R9C8 if the A's are true then there is no place for a 8 in column 6 so therefore all the A cells can't contain a 8 as a candidate so this means the B cells are 8.

[smurfdaddy]

You are not missing any obvious basic move, or even one of the most popular "advanced" moves. This needs a chain.

Code: Select all

+-------------------+-------------------+-------------------+
| 3     248   128   | 48    124   9     | 6     7     5     |
| 1247  5     1278  | 6     124   28a   | 9     3     128c  |
| 6     289   1289  | 5     7     3     | 12    18    4     |
+-------------------+-------------------+-------------------+
| 1257  2378  12578 | 9     68    4     | 12357 156   1237  |
| 47    3479  6     | 2     5     1     | 8     49    379   |
| 1245  2489  12589 | 3     68    7     | 1245  14569 129   |
+-------------------+-------------------+-------------------+
| 8     27    257   | 147   9     6     | 13457 145   137   |
| 79    6     4     | 178   3     5     | 17    2     89d   |
| 579   1     3     | 478   24    28b   | 457   89e   6     |
+-------------------+-------------------+-------------------+


There is a solution via "strong links" or "multi-coloring". Look at C6 and C9. They each contain only two candidates for <8>.

One or both of the cells labeled "b" and "d" must be <8>. Think about it! (If neither of them is <8>, both "a" and "c" must be <8>, a contradiction.)

So, R9C8 ("e") cannot be <8>, it must be <9>, and this solves the puzzle.

This pattern is sometimes called a "fork". It is two strong links that almost form an X-wing.

Best wishes,

Keith

[Cec]

Hi smurfdaddy,

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Cec