To guess or not

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To guess or not

Postby Guest » Fri Jul 29, 2005 2:49 am

In a puzzle I am completing I have come to a fork in the road. I can not see a definite next step. Everywhere I try there is at least a choice of two places to put a number. Now I can choose one of these, go down that road and if it is wrong I will know for sure that the other road was the correct one. Now the Q is. Should you be able to go through the whole puzzle without having to choose between 2 different paths. In other words. Is there always one Number that I can put in that is definitely right.
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Guessing

Postby tom375 » Fri Jul 29, 2005 5:14 am

Hi Terry

I'm a "newbie" to Sudoku, still struggling, but from reading elsewhere on this website I've learnt that Pappocom puzzles have only one solution and guessing or "trial & error" should not be used.

Do you want to write your puzzle here and see if someone can help?
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Re: Guessing

Postby Guest » Fri Jul 29, 2005 11:52 am

tom375 wrote:Hi Terry

I'm a "newbie" to Sudoku, still struggling, but from reading elsewhere on this website I've learnt that Pappocom puzzles have only one solution and guessing or "trial & error" should not be used.

Do you want to write your puzzle here and see if someone can help?

Thanks Tom,I dont know how to put my puzzle on here. I kmow thier is only one answer but to get there I still have the choice of two paths when I feel there should be always one difinite path.
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Postby scrose » Fri Jul 29, 2005 1:30 pm

Just type the puzzle into your message. You can use asterisks or zeros to represent the empty cells.

*71 8** ***
*** **2 1**
3*5 *** **6

*6* 2*1 **8
*** 7*6 ***
8** 5*4 *3*

7** *** 4*2
**2 1** ***
*** **7 31*

Or you can use the code tags to get a fixed-width appearance.

Code: Select all
 . 7 1 | 8 . . | . . .
 . . . | . . 2 | 1 . .
 3 . 5 | . . . | . . 6
-------+-------+-------
 . 6 . | 2 . 1 | . . 8
 . . . | 7 . 6 | . . .
 8 . . | 5 . 4 | . 3 .
-------+-------+-------
 7 . . | . . . | 4 . 2
 . . 2 | 1 . . | . . .
 . . . | . . 7 | 3 1 .

Once you post your puzzle, someone will surely be able to give you a hint.
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Re: To guess or not

Postby Guest » Fri Jul 29, 2005 10:34 pm

terry wrote:In a puzzle I am completing I have come to a fork in the road. I can not see a definite next step. Everywhere I try there is at least a choice of two places to put a number. Now I can choose one of these, go down that road and if it is wrong I will know for sure that the other road was the correct one. Now the Q is. Should you be able to go through the whole puzzle without having to choose between 2 different paths. In other words. Is there always one Number that I can put in that is definitely right.

*59*6***8
**17*89**
*84*9**3*
*****7694
867924513
9456318**
*9**7****
***2*67*9
47**19*8*
NOw this is where I got up to. I have seen the completed solution so I am sure this is correct. What I need to know is the next move. Good luck.
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Postby simes » Fri Jul 29, 2005 10:52 pm

The next move is (7,9) = 1... or do you want to know the reasoning behind it also?!

in which case, you need to look at a pair in box 8 and another in row 3.

Simes
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Postby Guest » Mon Aug 01, 2005 11:20 pm

Thanks a million Simes. Teh penny finally dropped. I am breathing again. Now I can be sure there is always one move which is a certainty. Bring on the next one. Thanks again. Terry.
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Postby LimeyCliff » Mon Aug 29, 2005 5:49 pm

Simes,

You say that ROW 7 Col. 9 = 1
How do you verify this When 1 could be in ROW 7 Col 1
or ROW 7 Col 7 or Row 7 Col 9

Cliff
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Postby Pat » Tue Aug 30, 2005 12:10 pm

-

LimeyCliff wrote:Simes,

You say that ROW 7 Col. 9 = 1
How do you verify this When 1 could be in ROW 7 Col 1
or ROW 7 Col 7 or Row 7 Col 9

Cliff


the 1 for c9 is in r3 or r7

but the r3 possibility is removed when you notice the 6,7 duo in r3[c1,c9]

- Pat
-
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Postby LimeyCliff » Tue Aug 30, 2005 6:42 pm

Pat,

I still cannot find the logic in your hints.

First let me say. I ran across this same puzzle three years ago and worked on solving it at that time. I spent many hours over an extended period and failed to arrive at the correct solution. At that time I decided it was unsolvable so I placed the puzzle in my unsolved files. Being a Visual Basic programmer I wrote a program to do the puzzles on. The program will not show how to solve puzzles but will give the solution if it is a valid puzzle. After entering this puzzle into the program it showed it was indeed a valid puzzle. Several times I tried to solve the puzzle but failed. When I saw the first post on this site I noticed it right away and I decided that I would find the correct logic to solve it by.

I appreciate what you have posted and if you can spare the time maybe I can see where my logic is failing by posting back and forth. If you would rather not do this it will be okay.

Thanks,
Cliff
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Postby MCC » Wed Aug 31, 2005 10:40 am

LimeyCliff

First of all look at row 3:

{267}[8][4]{15}[9]{25}{12}[3]{12567}

There is a hidden pair 6,7 in (r3c1)and(r3c9)
This enables you to eliminate the other candidates from these two cells,
including a 1 from column 9.

Column 9 therefore (after the above eliminations) contains:

[8]{256}{67}[4][3]{27}{1256}[9]{256}

Only one cell contains a 1 and that is (r7c9)


There is a hidden pair in row 8:

{135}{13}{38}[2]{458}[6][7]{45}[9]

i.e., 4,5 this enables you to eliminate the 8 from (r8c5) leaving an 8 to be placed in (r8c3).


Hope this is clearer for you.
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Postby LimeyCliff » Thu Sep 01, 2005 3:12 am

Voila,

Thanks for all the help that made it possible for me to solve the puzzle.

Cliff
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