The New Sudoku Players' Forum

[Pi]

I entered this sudoku onto a spreadsheet i wrote which aids sudoku's and usualy allows me to do a fiendish in around 2:20, i then came to a stalemate point when my computer told me that no squares had a positive number to put in them and that i would have to use trial and error, is this true or did anyone find a way of solving this using coventional methods

[Animator]

Why don't you post your grid then?

[Pi]

As only a minute after posting my message i was asked for my grid here it is,
At the start
**6*8**3*
*****7***
4**3*2*8*
59*7**4**
*4*****7*
**2**5*19
*8*4*3**6
***5*****
*3**6*2**
Then i got to
**6984*3*
8*36*7924
4*93*268*
598731462
341296*7*
**2845319
*8*4*3**6
***5****3
*3*16*2**
If you know another way to solve this please let me know
Pi.

[Animator]

Look at column 1, column 2, and column 3. Look closely at the number 7. Decide what box can have the 7 in what column.

If you figured that out correctly, then you can fill in r9c1

[Pi]

I still don't see how i could have known where the sevens were even after i finished it by trial and error

[Animator]

Take a close look at column 3.

Now here are some question you should ask yourself...

What rows can have the number 7 in that column?

In what box are all those rows located?

What does this mean for column 1 and column 2 of that box? can they have the number 7? or would that result in an incorrect grid/solution?

Update: A small note though, at this point it is impossible to tell the exact cell which holds the number 7. But you don't need to know that yet, by the knowledge of the number 7 you can fill in another cell, which ends up with only one valid candidate.