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Tough Sudoku for 26/July/2011

                 
                 
                 
                 
                 
                 
                 
                 
                 

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

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Sudoku Solving Techniques

Submitted by: sudoku lover

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Looks like quite a trek!
26/Jul/11 12:09 AM

SE=7.2

1)SSTS to UP=29
2)(7)a6=(7-5)i6=i7-(5=6)d7-d4=(6)a4,=>a4<>7
3)(89=2)bc8-(2=9)c6,=>c9<>9.UP =81
26/Jul/11 12:34 AM
still trying to find suitable TT 8.x, takes time, have to solve to make sure not too easy and not too long winded.
26/Jul/11 1:38 AM
SE 7.2
1) SST to UP29
2) (2=9)c6-b56=b8-(9=2)e8 > -2c8; UP37
3) (5=7)i6-a6=(7-6)a4=d4-(6=5)d7 > -5i7; UP81
26/Jul/11 2:28 AM
test your skills. Show this SE=8.3 doesn't qualify as TT after one depth 3 AIC loop.
600000013705100400010004070007809040000000000080207900070500020004001608350000001
26/Jul/11 2:38 AM
this one seems very hard (haven't tried UR or DP deductions yet) so today's TT SE=8.4

090040000004508002008002340049000030700000005030000160053200800200403600000080020
26/Jul/11 3:40 AM
5+ aic for TT, too long.
26/Jul/11 6:07 AM
another fascinating interlockig UR puzzle, an SE=8.3 quicky is the T-Lite for the day (AIC + pattern):

040000050906304001000000709000000007200809004030040900080021000001080000002003600
26/Jul/11 7:10 AM
the T-Lite:
1. SST to UP33
note: aur(36)eh56
note: aur(28)gh68::(145)g356=(36)h56
2. (9=4)c3-(145)g356=(36)h56-(36)e56=(169')e179 > -9d3b1, SSTE
/ SDQ(15679)d7e1789, -7e5, UP81
26/Jul/11 12:41 PM
The T-Lite (not so lite for me):
1. Unique possibilities to 32.
2. Whether e56=36;OR e7=6,d7=5,e8=7;f4=7.UP33.
3. Whether e56=36,h6=8(to avoid the 36 UR),h8=2;OR e7=6,d7=5=b8,e9=1,e1=9,b1=7=c5,c9=8,c4=5;i4=2.UP81.
kobold, your reference to the 28 UR is a bit erroneous, because 2 is locked at hi4. A 2 at gh6 is illegal.
26/Jul/11 3:06 PM
Alfred, I reached UP33 with 2:df9,gh8,dfgh6,fhi4,gi3 - no lock until you deduce +7f4 (the SDQ pattern) but that is beside the point!. A UR is always "illegal" and the SIS are true whether or not you prove some of the digits in the UR are false - this relation remains true up to and More...
26/Jul/11 3:53 PM
look at it this way, after the lock, removing 2 from gh6, it is still true that to avoid a UR (28)gh68, an +8g6 => (36)h56 and +8h6 => (145)g356.
26/Jul/11 4:25 PM
Ok. I thought you had (4)f7 as your UP33rd. I have 25UPs given;+ 7 new UPs (b6=2,d4=1,g9=3,h17=14,i19=18),making a total of 32 at step 1.






26/Jul/11 5:13 PM
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