Tough Sudoku

Gath has not come to his senses regarding the Sudoku blog that he lets me have on this site, so I thought that I better add another page soon.

I have decided to post a complete demonstration of how I solve a Tough Sudoku.

You can access this new blog page, Forbidding Chains 102 The Practice, through the link in the upper right column under the heading 'Check out the Sudoku Blog'.

I am in your debt, if you grace the blog with your presence!

It's Mr. Ed

Another interesting photo, Keyan.

Love the photo!! Would be interested to know where it was taken. Our horses live indoors (the school's, not mine personally...if only!!!), so I'm assuming this is a more temperate climate. Wonderful creatures. 'The best thing for the inside of a man is the outside of a horse.' Oft quoted, and attributed to Winston Churchill. As a new rider (a year and a half), I can relate to this!

22:46 night all!

Giddyup. I love horses.

Good morning to all! You even got them to pose and smile for the camera Keyan!

Quite the posers.

8:09...but one error. Oh well..try again tomorrow.

1) Start 23, Unique Possibilities to (UP) 28.
2) Locked 4s at hi7 forbid f7=4.
3) x-wing: 5s at c46, g46 forbid bdeh4=5, befh6=5.
4) The wraparound chain f7=5 == f7=2 -- f1=2 == e1=2 -- e1=5 == e9=5 forbids d9=5, f56=2, e1=68.
5) Naked triplet d9=29, h9=19, i9=129 forbids a9=19, b9=19, e9=129. UP 33.
6) e9=6 == e2=6 -- c2=6 == c8=6 forbids f8=6, ab9=6. UP 81.

7:58
It went well this time! Wasn't so difficult.
And picture is lovely; I love horses

33 minutes. Not too difficult. I'm just slow at finding short enough chains to forbid enough possibilities. Working on possibilities of 1 on column e, and fives of bottom right and top middle regions finally did it for me. Looks like many more steps than in Clark's solution, so I'm not gonna bother reworking the steps to write it down as a proof.

Rider at the gate ...by a John Macefield

'Who goes there?' said the guard at the gate.
'What is the news, that you ride so late?'
'News most pressing, that must be spoken
To Caesar alone, and that cannot wait.'

13.44

Nosey noses. :)

Your photos are always interesting, Keyan. Horses can be so curious.

Same as Clark's, different starting candidate on the wrap around:
1) Start at 23, Unique Possibilities to (UP) 28.
2a) locked 4's at df8, forbid f7=4
2b) x wing on 5's at cg46, forbids bdeh4=5, befh6=6
2c)f7=2==f7=5--e9=5==e1=5--e1=2==f1=2, forbids f56=2, d9=5 and e1=6
2d) triple 129 at d9=29,h9=19 and i9=129, forbids ab9=19, d9=129. UP 33.
3) fc on 6's, e9==e2--c2==c8 forbids ab9=6, f8=6. UP 81.

Thank you Steve for your explanation of wrap around chains, and also your method for searching for forbidding chains in blog 102!

Great photo Keyan, who goes there! why you do of course click click. Found this tough easier than most.

Cute Picture!

hello Mr & mrs ed.
simple tough today, all unique possibilities!

sorry, i used used wrong terminology above - not unique possibilities, but puzzle comes out very easily, similar to a 'hard'. Never been good at the terminology..... seem to usually work out the puzzles however, probably much slower than most of you, but most enjoyably!

Excellent instructions on your blog page,Steve! Almost makes me want to remember the terminology! Certainly makes sense when you painstakingly put it down like that - thank you!

19:09

Just saw this. Celia, the stable is in California...definitely more temperate!

I did this puzzle on 1/19 (back from vacation) but had to comment because, like Jen, I did it without fc's (I think), possible the first tough I've completed without guessing or help from someone's proof.

Great photo. I, too, love horses.

Oops - 'possibly'!

Dec. 22, 2007.

SE=7.0

36:10.