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Tough Sudoku for 19/July/2010

                 
                 
                 
                 
                 
                 
                 
                 
                 

Choose a number, and place it in the grid above.

  1 2 3 4 5 6 7 8 9
Check out the latest post in the Sudoku Forum

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Submitted by: Gath

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1.UP=25 (record for almost hidden pairs in a chain?)
2.(1)g6 = HP(14)g13 - (2)g1 = HP(26)ac1 - HP(17)c13 = (1)c45 => b6<>1 UP=52
3.(5)h3 = a3 - c2 = c7 - (5=3)a8 - b9 = h9 => h79<>5 UP=81.
19/Jul/10 12:22 AM
What a gorgeous vantage point, Wendy!
19/Jul/10 12:41 AM
I need to study farpointer's step 2 closely. I did the step from UP25 to UP52 in "if..then" language as follows.

Goal: Eliminate 2 from g1. If g1=2, then g3=4 and g6=1. This creates a 14 pair in c45. At this point 7 is the sole remaining candidate for both c3 and d3, and we have More...
19/Jul/10 3:37 AM
11:47 to you all from Portland, Oregon.

Lovely, Wendy.
19/Jul/10 3:55 AM
(1)g6.....HP(14)g13..............
..........(2)g1.........HP(26)ac1
(1)c45..................HP(17) c13

represented as a matrix. rows are strong and columns are weak. cf. Steves' blog: each row contains at least one true entry; each column contains (except first) at most one true More...
19/Jul/10 4:25 AM
it's like a jigsaw puzzle. you slot 3 or 4 a == b pieces into the matrix aligning weak links between pieces, aiming for gold in the first column.
19/Jul/10 4:32 AM
...of course, it's better start with two pieces that could yield gold in the first place, to avoid wasted effort.
19/Jul/10 4:52 AM
loops as matrix:
perfect loop => a is true
a...b....
....c...d
a.......e
wrapped loop a -- f => c == b & e == d
a...b....
....c...d
f.......e
19/Jul/10 5:50 AM
farpointer: your technique of using groups is so powerful! Very elegant!
19/Jul/10 6:22 AM
31:30
19/Jul/10 7:40 AM
Ah, beautiful Denmark, a stone's throw from Albany. A lovely little town that was virtually taken over by the hippies during the 70's & 80's. There are still quite a few around but it's now quite popular as a retirement town with people from the country and Perth retiring there.
19/Jul/10 11:03 AM
Oh Anne and here I was thinking the photo was taken overseas. lol
19/Jul/10 3:08 PM
A very beautiful piece of coastline!!! Thanks Wendy for the pic, and Anne for the info!
19/Jul/10 3:09 PM

SE=7.2
10/Sep/10 11:05 PM
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