## Can this puzzle be solved logically?

Advanced methods and approaches for solving Sudoku puzzles

### Can this puzzle be solved logically?

Hi all, i just started sudoku for 2 days and i'm just wondering if anybody has come across any puzzle that is impossible to solve without trial and error?

For this puzzle, i think i've went through almost all the logical processes.

* * * * 7 * 9 * 8
* * * * * * * 3 2
5 * * 1 * * 6 * *
7 * * * * 2 * * *
* * 4 5 * 8 1 * *
* * * 6 * * * * 5
* * 2 * * 3 * * 9
9 8 * * * * * * *
4 * 7 * 5 * * * *

* 4 6 * 7 5 9 1 8
1 7 9 * * * 5 3 2
5 * 8 1 * 9 6 * *
7 * * * * 2 * * *
* * 4 5 * 8 1 * *
8 * * 6 * 7 * * 5
6 * 2 * * 3 * * 9
9 8 * * * * * * *
4 * 7 9 5 * * * *

From then on, the way i completed the puzzle was to fill in 1 of the 2 possible number for r1c1. Got to some problems 10 minutes later then used the 2nd possible number. Can anybody figure out a way to solve this without spending the 10 minute with trial and error? Thanks in advanced.
Bunnybuck

Posts: 15
Joined: 13 June 2005

Have a closer look at r3c5
angusj

Posts: 306
Joined: 12 June 2005

in box2, i have narrowed down my the possibility to

23 7 5
48 468 46
1 23 9

i still cannot see how to decide which number (2 or 3) to put in r3c5
Bunnybuck

Posts: 15
Joined: 13 June 2005

Take a really good look at the number 1.

Where can it go in box 5?
What does this mean for box 8?
Where can it go in box 9?

What do you conclude out of the possible position of box 8 and box 9? As in, where can it go in box 7?
Animator

Posts: 469
Joined: 08 April 2005

Thanks a lot animator, i see it now. I actually went through step 1,2 and 3 before, but failed to notice the last step in box7. Must be my clogged-up brain due to 4 consecutive hours of sudoku last night.

This game rocks
Bunnybuck

Posts: 15
Joined: 13 June 2005

### Re: Can this puzzle be solved logically?

Bunnybuck wrote:Hi all, i just started sudoku for 2 days and i'm just wondering if anybody has come across any puzzle that is impossible to solve without trial and error?

just wondering..
Bunnybuck

Posts: 15
Joined: 13 June 2005

Yes. (If you look through other threads in this forum, you'll find examples.)
Last edited by simes on Sun Dec 11, 2011 2:36 pm, edited 1 time in total.
simes

Posts: 324
Joined: 11 March 2005
Location: UK

Bunnybuck,
Is this what you got?

3 4 6 2 7 5 9 1 8
3 4 6 2 7 5 9 1 8
1 7 9 8 6 4 5 3 2
5 2 8 1 3 9 6 4 7
7 5 1 3 4 2 8 9 6
2 6 4 5 9 8 1 7 3
8 9 3 6 1 7 4 2 5
6 1 2 4 8 3 7 5 9
9 8 5 7 2 1 3 6 4
4 3 7 9 5 6 2 8 1
havingfun

Posts: 2
Joined: 17 June 2005

That looks right -- minus the duplicate row 1, of course.
scrose

Posts: 322
Joined: 31 May 2005

After some time, I ended up with that. This is a really hard sudoku!
IQ

Posts: 6
Joined: 27 May 2005