huh? leap-of-faith?

Advanced methods and approaches for solving Sudoku puzzles

huh? leap-of-faith?

Dear Every One,

On today's puzzle (graded as a difficulty of 4 in a scale of 1-5), I safely got to a point where I could get no further. Hmmm. I am illogical and somewhat slapdash by nature, so my tallies (that is, the numbers that empty boxes could be) can be way off. I ruthlessly preened my sheet again and was still where I could get no further.

I took a photocopy of the sheet-where-it-seemed-I-was-still-safe and proceeded on the copy to make a 'leap of faith' to see what path that would take me along. Bingo. The puzzle was solved. Hmmm. When I cross-checked the skeleton puzzle on the Puzzle Solver, the puzzle solver agreed with the numbers I had put in.

I didn't need to scuttle back to my Safe Sheet to try another way, but does this not seem strange, that I should have stumbled on the way through by hapchance?

Hmmmmmm.
Magpie
magpie

Posts: 11
Joined: 21 September 2005

Not especially. I presume you chose a cell that only had a few (probably 2) candidates, so you had fairly good chances of getting it right. I don't know where your sudoku came from, but if it had multiple solutions (i.e. it was a 'bad' puzzle) then you might have been guaranteed a solution.
PaulIQ164

Posts: 533
Joined: 16 July 2005

Re: huh? leap-of-faith?

magpie wrote:does this not seem strange, that I should have stumbled on the way through by hapchance?

I would say it this way: Yes, it does seem strange; but surprisingly, it may be more the rule than the exception that a sudoku should have at least one "key cell" (i.e. one with two candidates such that the correct one leads to a solution using only naked- and hidden-singles).
r.e.s.

Posts: 337
Joined: 31 August 2005

thanks

Thank you, Paul, for your careful note. Do you have an IQ of 164? Wow.

I am going to attempt this puzzle again (I did check it against a computer solution on a different website and it came out the way I had completed it) and carefully -- very very carefully -- keep a record of what I did (which column, which row) when I did it so that I don't have to use the leap-of-faithlessness (for that's what it is, when one uses luck) to arrive at the solution.

I suspect it's my tallies in the beginnng.

Best regards,
Magpie
magpie

Posts: 11
Joined: 21 September 2005

I sometimes use that technique to convince myself the puzzle, as I have entered it and considering the things I have done so far, actually has a solution.

But assume you pick a cell to guess that has values {25}. You pick 2 and get a solution. Well, you also have to pick 5. You should now NOT find a solution. It gets tougher if you have to do multiple guesses. Say you pick 5 and get to a point where you have to guess again. Now you have to exhaust all those guesses.

It is much easier to use a computer program which automatically solves the problem and tells you if the solution is unique. But I enjoy torturing myself and doing it the hard way.

Actually not so hard: I wrote a program that allows easy saving of progress (www.SuDoku.funURL.com). You could have the honor of being the only other person in the Universe to try that program.

My SuDoku Scratch Pad does not actually solve the puzzle, that's your problem, but it does make it easier to get to the real challenges.

Mac
QBasicMac

Posts: 441
Joined: 13 July 2005

thanks, everyone

Thank you for your careful replies. This marvelous game, Sudoku.

I am almost certain that it's my tallying of possible numbers that leads me astray at the times I get led astray. If my pencil is sharp enough, if there is enough scrap paper to tally on, if (when the tallying is set), I then sharpen all my pencils again and take off through this wonderful Sudoku maze and bingo! It works.

My husband can do the same puzzle I am trying to do and it takes him, say, 2 hours and it takes me 2 days. Our 9 year old grandson told me this past Saturday, "If it takes Grampa 2 hours and it takes you 2 days, then it would take me 2 weeks! Don't feel bad, Dee Dee [my name to the grandchildren]." Such charm. He's a smart child and my husband expects he'll be able to knock these off in no time.

3 cheers, Every One. Thanks again for your replies.

Magpie
magpie

Posts: 11
Joined: 21 September 2005

Magpie, 'hapchance' is a great word - did you make it up or do you have some ancient old cobwebbed dictionary from days of yore?

Ocean, I tried your scratch pad. It's cute but not very forgiving if you enter wrong clues. After the third 'clear all' I actually gave up - recommended for accurate users! Not a criticism, just a comment.
emm

Posts: 987
Joined: 02 July 2005

[quote="em"] Ocean, I tried your scratch pad. It's cute but not very forgiving if you enter wrong clues.
[/quote]

"Ocean"? Did you mean me? (I am the only one that posted a reference to a scratch pad)

If so, thanks for trying it. If you have any suggestions regarding "forgiving", I would welcome them. Maybe a backspace button that would undo whatever was done in the previous move. Tough to program but would try it if you think that is important.

What I do, if I am guessing (rather than just making a mistake, which is actually pretty hard to do with minimal care), I first do a save-game.

If not me, could you provide a link to "Ocean"s scratch pad. I have tried many and like to see what others do.

Mac
QBasicMac

Posts: 441
Joined: 13 July 2005

hapchance

Dear em,

Thank you for your kind note.

"Hapchance" is a word I heard centuries ago, it seems, but I can't remember where it was (or where I was when I heard it).

It works, doesn't it? Hapchance.

Best regards,
Magpie

Resolution to self: be - brutally - careful - when - marking - possible -numbers - in - the - row/block/colums or the magic won't work.
magpie

Posts: 11
Joined: 21 September 2005

QBasic, yes, I meant you! Sorry for calling you Ocean - must have water on the brain! If you forgive me, then I won't take that bit about minimal care too personally either.

I have to admit it - backspace buttons are some of my closest friends, but I have no idea what it takes to write a program and I'd hesitate to suggest that you do that without getting someone else to check it out first. It might just be me!
Last edited by emm on Tue Oct 04, 2005 4:31 pm, edited 1 time in total.
emm

Posts: 987
Joined: 02 July 2005

Magpie - you can't possibly be a granny!! You're the nicest thing on the site, as I'm sure your husband and grandson agree, being the discerning chaps that they are. More power to your Su Doku elbow.

em - "hapchance" might be a corruption of happenstance (Oxford English Dictionary - coincidence), which is a blend of happen and circumstance, is said to be of 19th century origin and is apparently used chiefly in North America!
9X9

Posts: 100
Joined: 26 September 2005

9X9 !

What kind words, 9X9! I don't deserve them, for I am a holy terror when my columns don't match up and I frighten the horses on the street until they do.

But thank you, just the same.

Magpie
magpie

Posts: 11
Joined: 21 September 2005