The New Sudoku Players' Forum

[Carcul]

Code: Select all

 *------------------------------------------------------------*
 | 2      3      6   | 157    17     4    | 58     578    9   |
 | 9      1      4   | 8      67     567  | 235    257    357 |
 | 7      5      8   | 3      29     29   | 6      4      1   |
 |-------------------+--------------------+-------------------|
 | 3      68     129 | 1259   1289   1259 | 7      1256   4   |
 | 5      68     129 | 4      12789  1279 | 123    126    36  |
 | 4      7      12  | 1256   126    3    | 125    9      8   |
 |-------------------+--------------------+-------------------|
 | 16     2      3   | 1679   4      1679 | 158    15678  567 |
 | 16     9      7   | 16     5      8    | 4      3      2   |
 | 8      4      5   | 1267   3      1267 | 9      167    67  |
 *------------------------------------------------------------*


[r6c5]=6=[r6c4]-6-[r8c4]=6=[r8c1]=1=[r7c1]-1-[r17c7]-5-[r6c37]-
-1,2-[r6c5],

and so r6c5<>1,2 => r6c5=6 and the puzzle is solved.

Carcul

[Del]

To Carcul,
I am not able to follow the logic of your reasoning, probably because I do not understand the form of notation used in the forum.
I see that if r6c5=6 then r6c4 does not have a 6 and that the 6 in col.4 must lie in box 8; in r7c4 or r8c4 or r9c4 since the 6 in box 2 would be in col.6.
If r8c4=6, (why do you choose this cell out of the three possibilities?), then r8c1=1 and r7c1 does not contain 1. After that I am lost. If you have the time and patience would you please explain in English prose the gist of your manner of deduction.
A comparison of a lucid explanation with your notated form may enable me to follow this methodology. Alternatively perhaps there is a web page which describes the system.
Regards,
Del.

[ravel]

The nice loop notation is not easy to read without explanation.
E.g. [r6c5]=6=[r6c4] means that there is a strong link in 6 between the cells r6c5 and r6c4, i.e. r6c5=6 <=> r6c4<>6 and r6c5<>6 <=> r6c4=6. You always can read it from left to right and from right to left.

The deduction can be explained alternatively as:
r6c5<>6 => r6c4=6 => r8c4=1 (r8c4<>6) => r8c1=6 => r7c1=1 => pair 58 in r17c7 => (r6c7<>5) pair 12 in r6c37 => r6c5<>12, i.e.
if r6c5 is not 6 (then 1 or 2), then it is also not 1 or 2, a contradiction => r6c5 must be 6.