The New Sudoku Players' Forum

[Jeff]

My friend rmadhusudanan,
Sorry that I have confused you. This was Mac's grid and I have just copied it to show him the format. Your logic is excellent anyway.

[rmadhusudanan]

My New friend Jeff,

Thanks. I am new to this forum and I hope I have not given any offence.

Do pass on any brain teasers for me to enjoy solving them as you all must be doing for all these years.

R Madhusudanan
India

[QBasicMac]

When you eliminate this candidate you will easily see that R7C6 CAN BE ONLY 6.

Here is the original puzzle and the solution (In strange format to make comparisons easy)

1 - Row Numbers
2 - Original Puzzle
3 - Solution
4 - What I posted with my question

Code: Select all

111111111 222222222 333333333 444444444 555555555 666666666 777777777 888888888 999999999
-3-5-487- -----7--9 4-----5-6 -1-8--26- ----6---- -63--9-8- 8-1-----5 3--9----- -964-8-3-
639524871 152687349 487391526 915843267 748162953 263759184 871236495 324975618 596418732
63-5-487- 1--6-7349 4-----5-6 91-8--26- ----6-95- -63--9-8- 8-1----95 3--9----8 -964-8-3-


I made some simple pencilmark eliminations and then posted my pencilmarks, here reformatted for Jeff.

Code: Select all

+----------------+----------------+----------------+
| 6    3    29   | 5    129  4    | 8    7    12   |
| 1    258  258  | 6    28   7    | 3    4    9    |
| 4    278  2789 | 123  12389123  | 5    12   6    |
+----------------+----------------+----------------+
| 9    1    45   | 8    3457 35   | 2    6    347  |
| 27   248  248  | 1237 6    123  | 9    5    1347 |
| 257  6    3    | 127  124579    | 17   8    147  |
+----------------+----------------+----------------+
| 8    247  1    | 237  237  236  | 46   9    5    |
| 3    2457 2457 | 9    1257 1256 | 46   12   8    |
| 25   9    6    | 4    125  8    | 17   3    127  |
+----------------+----------------+----------------+


In response, em said "There are 2 simple moves to get beyond your posted candidates. A naked triple in row three and an Xwing in r69c15. After that it’s colouring or chains I’m afraid."

So in honor of the X-Wing, I eliminated 5 from r8c5 and r4c5 and in honor of the naked triple, I eliminated 123 from r3c5 and 2 from r3c2 and r3c3.

Now I was prepared for colouring or chains, I'm afraid.

Your observation that r8c5=1 > r3c8=1 > r1c5=1 (impossible) was kind of appealing although I normally avoid chains. So, I removed the pencilmakr 1 from r8c5. This left me with the following pencilmarks.

Code: Select all

+----------------+----------------+----------------+
| 6    3    29   | 5    129  4    | 8    7    12   |
| 1    258  258  | 6    28   7    | 3    4    9    |
| 4    278  2789 | 123  12389123  | 5    12   6    |
+----------------+----------------+----------------+
| 9    1    45   | 8    3457 35   | 2    6    347  |
| 27   248  248  | 1237 6    123  | 9    5    1347 |
| 257  6    3    | 127  124579    | 17   8    147  |
+----------------+----------------+----------------+
| 8    247  1    | 237  237  236  | 46   9    5    |
| 3    2457 2457 | 9    257  1256 | 46   12   8    |
| 25   9    6    | 4    125  8    | 17   3    127  |
+----------------+----------------+----------------+


Here is where you say that if I eliminate the 1 (which I did) that I will easily see that R7C6 CAN BE ONLY 6.

The pencilmarks I show lead to the solution easily by T&E. If you have different ones, is there some more simple chains or something that will lead to the place where I "easily see" that r7c6=6?

Thanks for your patience.

Mac

[Jeff]

I am new to this forum and I hope I have not given any offence.

No offence whatsoever.

Do pass on any brain teasers for me to enjoy solving them as you all must be doing for all these years.

Tso, could you help this gentleman out as I know you have plenty of good ones in your library.

[Jeff]

[I made some simple pencilmark eliminations and then posted my pencilmarks, here reformatted for Jeff.

Nicely done, thank you.

[rmadhusudanan]

Dear Mac

I have to learn much of the language used.

What is T&E. Is is trial and error?

Please direct me to where i can learn what is coloring as i am not familiar with this.

Thanks in advance

Madhusudanan

[Ruud]

T&E is indeed Trial & Error. A very ugly term to some people.

Colouring is best described here: http://www.simes.clara.co.uk/programs/sudokutechnique12.htm

Ruud.