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#1 2007-07-06 11:07:19

forsmarts
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From: Minsk
Registered: 2007-05-29
Posts: 195
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Fortress Sudoku

Fill in the grid following the standard Sudoku rules. There is a fortress inside the grid. When two cells are divided by its wall then the cell inside the fortress must contain greater number.
http://forsmarts.com/forum/img/puzzles/fortress01.gif

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#2 2007-07-06 11:37:09

Andrey Bogdanov
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From: Moscow
Registered: 2007-05-30
Posts: 355
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Re: Fortress Sudoku

It's not difficult, but pleasured.
Thank you.

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#3 2007-07-09 12:18:13

Mango
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From: Berlin
Registered: 2007-06-18
Posts: 3
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Re: Fortress Sudoku

It's a nice puzzle, the idea is also quite pretty. I agree with Andrey - it's not difficult, but I've got satisfaction by solving it.

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#4 2007-07-17 19:58:43

Pyrrhon
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Registered: 2007-07-16
Posts: 8
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Re: Fortress Sudoku

Nice variant. This fortress sudoku should be more difficult:

http://www.sachsentext.de/gif/fortress_sudoku1.gif

Last edited by Pyrrhon (2007-07-17 19:59:05)

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#5 2007-07-23 17:05:13

forsmarts
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From: Minsk
Registered: 2007-05-29
Posts: 195
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Re: Fortress Sudoku

Pyrrhon wrote:

Nice variant. This fortress sudoku should be more difficult:

After many attempts I must confess - I couldn't solve it smile

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#6 2007-07-24 11:47:01

Pyrrhon
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Registered: 2007-07-16
Posts: 8
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Re: Fortress Sudoku

I'm not sure whether it is usual to give walkthroughs in this forum, but here is one for the last one. If you like to solve this puzzle yourself, then don't read further this message. For sure there are shorter ways to get the result. If you don't like standard sudoku techniques like x-wing or turbot fishs you can make the other fortress sudoku on my website.

Hidden single in C9 => R5C9=1
Hidden single in B6 => R5C8=5
R4C7>5, R6C8>5, => R4C7, R6C8 = {78}, R5C7, R6C7, R6C9 = {234}
R7C7<> 1, 2

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol1.gif

R6C7 > R7C7 => R6C7 = 4. R5C7, R6C8 = {23}
R6C7>R7C7, R7C7> 2 => R7C7=3, R5C7=2, R6C9=3
R5C2 < R6C2, R5C2<>1,2 => R5C2={34}
R4C2>R5C2, R4C2 <> 5, 7, 6, 9 => R4C2 = {4, 8}
Hidden Single in B4 => R4C1=2
R5C3 <> 1,2,3 => R5C3 > 3
R4C3>R5C3, R5C3 > 3 => R4C3> 4
R4C3<> 5,6,9 => R4C3={7,8}

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol2.gif

Naked Pair in R4 => R4C2 = 4, R5C2 = 3
R3C6>R3C7, R3C6 <> 6,8 => R3C6 = {7,  9}
hidden single 2 in C6 => R6C6 = 2
R7C4 > R7C3, R7C4 <> 3 => R7C4 > 3
R4C2 = 4, R4C2 > R3C2 => R3C2 = {1,2}
3 values in row 3 smaller R3C4 (this is R3CC3, R3C5, R3C2) => R3C4 > 3
R2C4>R2C3=>R2C4>3
Hidden Pair 1, 3 in C4 => R1C4, R4C4 = {1,3}

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol3.gif

R7C2 < R6C2, R7C2 <> 2, 3, 4 => R7C2 = 1, single R3C2 = 2
R5C3 <> 1,2,3,4,5 => R5C3 > 5
2 bigger cells in C3 (R4C3, R6C3) => R5C3 ={67}
R5C4>R5C3, R5C4 <> 8 => R5C4 > {79}
R7C5 <> 1, 2, 3 => R7C5 > 3
R7C4>R7C5 => R7C4 > 4
R6C4<>1,2,3,4,5,8 => R6C4 = {6,7,9}
Hidden Triple in R4 => R4C5, R4C6 = {1,3,5}

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol4.gif

R4C5 > R3C5 => R4C5 <> 1, R3C5 < 5
R3C5 <> 2 (R3C2), 4 of C4 in R2C4 or R3C4 => R3C5 = {1,3}
R6C3>R5C3 => R6C3 = {7,8,9}
R5C6>R5C7, R5C6 <> 2,3,5,6,8 => R5C6 = {4,7,9}
R2C2={89}
R3C3<R4C3, R3C3 <> 2,3,5 => R3C3 = {1,4,6}
R7C6 > R7C5 => R7C6 > 4
R8C5<>1, 2 => R8C5 > 2
R8C6>R8C5 => R8C6 > 3

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol5.gif

hidden pair 1, 3 in C6 => R4C6, r9C6 = {1, 3}
single in r4 => R4C5 = 5
3 cells greater as R7C5 in B8 (R7C4, R7C6, R8C4) => R7C5 < 7
R7C5<7, R7C5 > 3, R7C5 <> 5 => R7C5 = {4,6}

R1C5,R2C5 <> 1, 3 (naked pair in B2), 5, 6, 8 (naked singles)
4 of C4 in R2c2 or R2C3 => R1C5,R2C5 <> 4
=> R1C5,R2C5 = {2,7,9}
R2C6 > R2C5 => R2C5 ={2,7}

R2C4, R3C4 > 3, <> 2, 7, 9 (naked triple in B2), <> 6, 8 (singles)
=> R2C4, R3C4 = {4,5}
R3C4 <> 5 => R3C4 = 4, R2C4=5

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol6.gif


R3C3 < R3C4 => R3C3 = 1
Hidden Single in R1 => R1C4 = 1, R3C5 = 3, R4C4 = 3, R4C6 = 1, R9C6 = 3
Hidden triple in C4 => R7C4 = {6,7,9}
Hidden Single in B8 => R9C5 = 1
R2C5 < R2C4 => R2C5 = 2, R1C5 <> 2

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol7.gif

Hidden Single in R1 => R1C8 = 3, in C8 => R8C8 = 2, in R1 => R1C9 = 2, in B3 => R2C9 = 4, in R8 => R8C1 = 3

R8C5 <> 1,2,3 => R8C5 > 3 => R8C6 > 4
Hidden Single in C6 => R5C6 = 4
R5C6 > 4, R5C6 <> 6,7,8 => R5C6 = {5, 9}
R8C5>3, R8C5 <> 5,7,8, R8C5 < R8C6 => R8C5 = {4,6}
naked pair {4, 6} in B8 => R7C4 = {7, 9}
hidden single in C4 => R6C4 = 6
hidden triple in B8 => R7C6 = {5,7,9}
hidden triple in C5 => R5C5, R6C5 = {7,8,9}
R1C7 <> 1,2,3,4,5,6 => R1C7 = {7,8,9}
hidden pair 4, 5 in R1 => R1C1, R1C3 = {4,5}

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol8.gif

turbot fish with 7, strong links in B6 and R1, weak link in C7 => R6C5 <> 7
7 of B5 in R5 => R5C3 <> 7 = > R5C3 = 6
R7C8<R6C8, R6C8 <> 1,2,3,5 => R7C8 = {4,6,7}
7 of B 8 locked in R7 => R7C8 <> 7 => R7C8 = {4,6}
R7C1 <> 4,6 (naked pair in R7), <> 1,2, 3, 7 (singles) => R7C1 = {5,8,9}

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol9.gif

x-wing with 6, strong links in C2, C7 => R2C1, R9C1 <> 6
naked single in C1 => R3C1 = 6
hidden single in B3 => R2C7 = 6
hidden single in C2 => R9C2 = 6
hidden single in C2 => R2C2 =9, hidden single in B1 => R2C1 =7, R1C2=8,
in C8 => R7C8=6, in R7 => R7C5 = 4, in C5 => R8C5 = 6, in B9 => R9C8 = 4,
in R8 => R8C3 = 4, in C1 => R1C1 = 4, in R1 => R1C3 = 5
R8C5 < R8C6 => R8C6 = 9
single in C6 => R3C6 = 7, in B2 => R2C5 = 9, in R1 =>  R1C7 = 7 ...

http://www.sachsentext.de/gif/tmp/fortress_sudoku1_sol10.gif

Last edited by Pyrrhon (2007-07-24 11:48:52)

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#7 2007-07-25 13:29:32

forsmarts
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From: Minsk
Registered: 2007-05-29
Posts: 195
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Re: Fortress Sudoku

Pyrrhon, nothing to say, but "Well done!" Thank you!

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#8 2008-01-28 05:37:08

Katherine
Member
Registered: 2008-01-28
Posts: 20
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Re: Fortress Sudoku

It's a very interesting puzzle.some of the cells inside the fortress must larger than 3 cells beside.that's very usefull

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#9 2010-09-06 23:51:34

bobmarks
New member
Registered: 2010-09-06
Posts: 1

Re: Fortress Sudoku

Hmm very interesting I don't think Ive seen a fortess sudoku before, yes very well done

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