Can't solve hard puzzles

Advanced methods and approaches for solving Sudoku puzzles

Can't solve hard puzzles

Postby Cec » Tue Jul 19, 2005 7:50 am

kk
Cec
 
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Joined: 16 June 2005

Postby Cec » Tue Jul 19, 2005 7:58 am

Ignore previous message"kk". Message failure. I have typed replies twice, clicked 'preview' and/or 'submit' box but message doesn't go through. Any solution anybody?
Regards Bonsai Cec
Cec
 
Posts: 1039
Joined: 16 June 2005

Can't solve hard puzzles

Postby Cec » Wed Jul 20, 2005 1:52 am

Oops!! Yes I did goof on this and I deserve a kick up the backside from simes after his clear explanation on the formation of the x-wing pattern. Again I thank those who helped me and I'll stay with Angusj's description on this subject.
Regards Bonsai Cec
Cec
 
Posts: 1039
Joined: 16 June 2005

Re: Can't solve hard puzzles

Postby dick » Tue Jul 26, 2005 4:39 pm

cecbevwr wrote:Hi Suduko friends. I started the following hard (very hard?) puzzle:

*4* *5* ***
**6 **2 **9
58* 1*6 ***

*6* 82* ***
8** *** **5
*** *73 *8*

*** 7*9 *24
6** 3** 9**
*** *6* *7*
I got as far as this:

*4* 957 ***
**6 4*2 **9
58* 1*6 ***

*65 82* ***
8** 69* **5
*** 573 *8*

358 719 624
6** 348 951
*** 265 *7*

Looking at Blocks 3,6 and 9, ie columns 7,8 and 9, the following
candidates exist which I think is a "X -Wing" pattern which I don't
fully understand even after reading the explanatory notes from
www.angusj.com/sudoku/hints.php:

1238 136 12368
134578 134 9
2347 34 27

1347 13479 137
12347 13469 5
124 8 126

6 2 4
9 5 1
138 7 138

I suspect candidates 1,3 and 8, which appear in each of the four
corner cells, r1c7, r1c9, r9c7 and r9c9, provide the necessary
rectangular pattern for a valid X-Wing. However, from this
point on I am stumped!! I would appreciate help in explaining
to me which candidates can be eliminated so I can proceed
further.

For what it's worth, I enjoy solving these puzzles but become
frustrated when I can't. The help I get from this forum is what
keeps me interested to learn more hints to solve these puzzles

Regards Bonsai Cec


Try this: first label columns A,B,C,D,E,F,G,H,&I and rows 1,2,3,4,5,6,7,8,&9.
The following are the steps:
I8=1
I9=3
I4=7
I3=2
I1=6
D1=9
D2=4
E3=3
E2=8
F1=7
D5=6
D6=5
D9=2
E7=1
E8=4
E5=9
A7=3
B7=5
C7=8
G7=6
H3=4
G3=7
C3=9
H6=6 (CAN ONLY BE 6)
H4=9 (CAN ONLY BE 9)
C4=5 (CAN ONLY BE 5)
G4=3 (ROW 4 CAN ONLY BE 3)
A4=4
C9=4 (BLOCK CAN ONLY BE 4)
A2=7 (COLUMN CAN ONLY BE 7)
Note 1: C1 can't be 1 since columb A1 or B2 =1 (based on A9 or B9). Since 1 is eliminated from C1, then in column C row 6 can only be 1)
Note 2: C1 can't be 2 since A6 or B6 must be 2 or 9. therefore:
C1=3 (only remaining number that can fit)
C5=7
B2=1
A1=2
B5=3
A6=9
B6=2
A9=1
B9=9
B8=7
C8=2
G2=5
H2=3
H1=8
G1=1
G9=8
H8=5
F8=8
F9=5
COMPLETE !! REGARDS DICK
dick
 
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