Su Doku

[DougShrapnel]

Difficult sodukos, sometimes require guessing. The example I was refering to is when you the other 5 squares are filled out allready, and there is no way to find a solution to a square without guessing.

[posnera]

Again, referencing Janauarymute above, a properly constructed sudoku puzzle requires no guessing to complete it. If you are stuck in one box, the solution can be found by working another area. No guessing. Post an example that you thing "requires" a guess. I'm sure that there is a deductive solution.

I'm not trying to be a nit or to show off, but I never need to guess. I like doing the hard puzzles and needing to guess would kill the fun for me.

[DougShrapnel]

The insane soduko's from this site sometimes require quessing. It's not your cup of tea to do a "improperly" made soduko, so i guess you can ignore it. For a soduko purist as yourself you will also be disappointed to find that the puzzles aren't always symetrical. However, I'm not a purist and think that provided that a puzzle has a unique solution it is a soduko.

http://www.soduko.org/sudoku-play-online.php

[mostsmooth]

[ QUOTE ]
Difficult sodukos, sometimes require guessing. The example I was refering to is when you the other 5 squares are filled out allready, and there is no way to find a solution to a square without guessing.

[/ QUOTE ]
ive yet to come across a sudoku puzzle that required guessing. perhaps ive been lucky? i always do the evil level on websudoku.com

[DougShrapnel]

I haven't looked at it in depth, and I'm not sure if this one requires a guess. I am curious to see if you all are using any techniques that I am not. What techniques would you guys use from here?

<font class="small">Code:</font><hr /><pre>
8 7 6 1 4 5 9 2 3
9 6 8 3 7 4 1
3 4 1 9 2 7 5
8 7 4 1 2 3
3 5 2
2 3 8 9 6 1 5
8 7 3 6
3 6 7
6 4 7 8 3 2
</pre><hr />

edit for readability

<font class="small">Code:</font><hr /><pre>
8 7 6 1 4 5 9 2 3
x 9 x 6 8 3 7 4 1
3 4 1 9 2 7 5 x x
x x 8 7 4 1 2 3 x
x x x 3 5 2 x x x
x 2 3 8 9 6 1 5 x
x 8 7 x 3 x 6 x x
x 3 x x 6 x x 7 x
6 x x 4 7 8 3 x 2
</pre><hr />

[mute]

[ QUOTE ]
I haven't looked at it in depth, and I'm not sure if this one requires a guess. I am curious to see if you all are using any techniques that I am not. What techniques would you guys use from here?

<font class="small">Code:</font><hr /><pre>
8 7 6 1 4 5 9 2 3
9 6 8 3 7 4 1
3 4 1 9 2 7 5
8 7 4 1 2 3
3 5 2
2 3 8 9 6 1 5
8 7 3 6
3 6 7
6 4 7 8 3 2
</pre><hr />

edit for readability

<font class="small">Code:</font><hr /><pre>
8 7 6 1 4 5 9 2 3
x 9 x 6 8 3 7 4 1
3 4 1 9 2 7 5 x x
x x 8 7 4 1 2 3 x
x x x 3 5 2 x x x
x 2 3 8 9 6 1 5 x
x 8 7 x 3 x 6 x x
x 3 x x 6 x x 7 x
6 x x 4 7 8 3 x 2
</pre><hr />

[/ QUOTE ]

I'm pretty sure you made a mistake somewhere along the line. There are two 4's in column 5.

[DougShrapnel]

[ QUOTE ]
[ QUOTE ]
I haven't looked at it in depth, and I'm not sure if this one requires a guess. I am curious to see if you all are using any techniques that I am not. What techniques would you guys use from here?

<font class="small">Code:</font><hr /><pre>
8 7 6 1 4 5 9 2 3
9 6 8 3 7 4 1
3 4 1 9 2 7 5
8 7 4 1 2 3
3 5 2
2 3 8 9 6 1 5
8 7 3 6
3 6 7
6 4 7 8 3 2
</pre><hr />

edit for readability

<font class="small">Code:</font><hr /><pre>
8 7 6 1 4 5 9 2 3
x 9 x 6 8 3 7 4 1
3 4 1 9 2 7 5 x x
x x 8 7 4 1 2 3 x
x x x 3 5 2 x x x
x 2 3 8 9 6 1 5 x
x 8 7 x 3 x 6 x x
x 3 x x 6 x x 7 x
6 x x 4 7 8 3 x 2
</pre><hr />

[/ QUOTE ]

I'm pretty sure you made a mistake somewhere along the line. There are two 4's in column 5.

[/ QUOTE ]

Dangit, and I knew that was gonna happen. I'll triple check this time.

<font class="small">Code:</font><hr /><pre>
8 7 6 1 4 5 9 2 3
x 9 x 6 8 3 7 4 1
3 4 1 9 2 7 5 x x
x x 8 7 1 4 2 3 x
x x x 3 5 2 x x x
x 2 3 8 9 6 1 5 x
x 8 7 x 3 x 6 x x
x 3 x x 6 x x 7 x
6 x x 4 7 8 3 x 2
</pre><hr />
x's in order
R1
R2 (2,5)(2,5)
R3 (6,8)(6,8)
R4 (5,9)(5,6)(6,9)
R5 (1,4,7,9)(1,6)(4,9)(4,8)(6,8)(4,6,7,8,9)
R6 (4,7)(4,7)
R7 (2,4,)(2,5)(1,9)(1,9)(4,5)
R8 (1,2,4,,9)(2,4,,9)(2,5)(1,9)(4,8)(4,5,8)
R9 (1,5)(5,9)(1,9)

[DougShrapnel]

nevermind on this one no guessing required.

Squares R6C1 and R6C9 in row 6 and R7C1 and R7C9 in row 7 form a Simple X-Wing pattern on possibility &lt;4&gt;. All other instances of this possibility in columns 1 and 9 can be removed.
R5C1 - removing &lt;4&gt; from &lt;1479&gt; leaving &lt;179&gt;
R5C9 - removing &lt;4&gt; from &lt;46789&gt; leaving &lt;6789&gt;
R8C1 - removing &lt;4&gt; from &lt;1249&gt; leaving &lt;129&gt;
R8C9 - removing &lt;4&gt; from &lt;458&gt; leaving &lt;58&gt;