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14 Dec 2005 v.h. sudoku: solution

("!" means "good/hard move" )
("!!" means "very good/hard move" )

6b5 2i7
3f5! ( see column f )
3g6
1e6! ( due to 1 in cell a4, in box 6 the 1 should be in cel ...

13 Dec (vh) sdk
soln:

i use notations:

boxes (b1...b9):

box1 box 2 box3
box4 box 5 box6
box7 box 8 box9

columns (ca...ci) :

c c c c c c c c c
o o o o o o o o o
L L L L L L L L L
a b c ...

I managed to resolve 13 cells before resorting to compiling the
candidate profiles. Otheres may be able to do better.

Alan Rayner BS23 2QT

Alan,

i could do only 8 after which the position is

000 ...

My version of solution actually requires no guess at all:

02 Dec (h) sdk soln

initial position (26):

3a9 9e9 1f9 4i9 2d8 3h8
9b7 5c7 3d7 1h7
7b6 6d6 4a5 1i5
7f4 2h4
1b3 9f3 2g3 7h3
8b2 3f2 7a1 1d ...

This is my version:
we begin with evident moves:
01 6h1 02 6d7 03 6b4 04 6f6
05 7g4 06 8c1 07 8f5 08 8i9 (so much so good...)

now remove 2 as candidate from cells c8,c8; this creates pair c7,c8 ...

01 7a1 * (see cb+cc) (here i use as shorhand "see cb+cc" = "see column b and column c")
02 9f5 * (see cd+r4+r6) 3 7d5 (see r4+r6)
04 3e4 * (see cd+r3+r5) 05 4b9 * (see c1+r8+r9)
06 2b5 07 ...

1. actually i used only the "candidates" shown by program, it greatly reduces the "dirty" work, while the "logic" becomes almost automatical (at least for the easy/medium sdk's).

2. i had no purpose ...

Here's Nov 23 2005 (v hard) sdk's soln from the beginning:

01 3b5 02 3f7 03 3d2 04 3h4 05 6a8 06 2a2 07 2f5 08 2d3
09 1e3 10 8e7 11 4e8 12 5e5 ! 13 6e2 14 9d1 15 5f1 16 4b1
17 8a5 ! 18 ...

Nov 26 2005
(medium) sudoku
solutuon

1- 5: 3a3 2h4 2b3 2a9 4a5 8i5
6-10: 6g2 6c8 8b6 6b4 9e4 4f4
11-15: 5e3 3e6 7e7 5d6 4c3 5c2
16-20: 8a7 7a8 1g4 7c4 1c6 4g6
21-25: ...

Solution of Nov16 (hard) sudoku:

1. 8g8 * (* means that move can be done from the beginning)
2. 6i4 * 3. 6a1 * 4. 6c9 Now cells b4,f4 make pair 4,7, hence next 3 moves:
5. 5e4 6. 3g4 7. ...

Nov 24 sudoku (medium)
solution:

1. 3b8 * (* means that it can be done from the beginning)
2. 5a8 3. 6f7 * 4. 5g3 * 5. 3c5 6. 3f4 7. 9d3 ! (see 1-3 rows: b1,c1 have pair 5,9, hence no 9 in ...

Solution of Nov 25 sudoku

1. 2h3 2. 7d5 3. 6b1 4. 2f5 5. 2a6 6, 2c7 7. 2i9 8. 8c5
9. 8i4 10. 4e5 11. 6g5 12. 6h2 13. 7i7 ! 14. 7g3 15. 7a1 16. 7b8

Here i asked hint and get 8d8 which is rea ...

Dear sudoku fans,

While solving the sudoku i use chess-like notation:

columns l->r : a,b,c,d,e,f,g,h,i
rows d->u: 1,2,3,4,5,6,7,8,9

so d4 stands for cell r4c4, and 4a1 stands for move "put 4 ...