## Solution to Tarek's Fluid Drive #2

Advanced methods and approaches for solving Sudoku puzzles

### Solution to Tarek's Fluid Drive #2

Fluid Drive #2

Code: Select all
`   6 . . . . 9 8 . .   . 5 . . 3 . . . .   . . 2 5 . . . . 7   . . 7 . . . . . 9   . 1 . . . . . 2 .   4 . . . . . 3 . .   3 . . . . 8 6 . .   . . . . 4 . . 8 .   . . 9 7 . . . . 1`

My solution :

(1) ... (denotes use of SSTS, here including elimination of 3e6 by colouring).

(2) ?7f6...(?3a3...??)-3a3...-8f5(MC), -8e5(MC),
(?3a2...(?8b4...??) -8b4, 8c5...(?8f9...??) -8f9, 5f9...??)
-3a2, 4a2...?? -7f6.

(3) ?7h7...(?3a2...??) -3a2, 4a2...?? -7h7...

(4) ?3a3... -2g4(MC)...(?9g4, -5e6(MC), -5e9(MC)...(?8f3...??) -8f3,
6f3...??) -9g4, 1g4...?? -3a3, 4a3...

(5) ?3a8...?? -3a8...

(6) ?1c1...?? -1c1, 9c1, -4d4(MC).

(7) ?2g2...(?5g3...??) -5g3, 1g3...?? -2g2, 4g2, -4e6(X-Wing), -5k6(colours), -8e5(XY-Wing 568e1f39)...-6ce6(colours)...End.
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Comments: No trial steps rejected. I resorted to sub-sub-nets as this was the quickest and easiest way to go.
The use of these sub-sub-nets underlies the difficulty of this puzzle, which I found about equal to that of Fluid Drive #1.
gurth

Posts: 358
Joined: 11 February 2006
Location: Cape Town, South Africa

That was quick......

I'm afraid that the rest of the fluid drives are not on par with this one.........

Do you use uniqueness in your solutions gurth ? if not then fluid drive #4 should provide a challenge.

In the mean time I will look into the steps of Fluid drive #2 & see if there are any alternatives that can be provided....

tarek

tarek

Posts: 2699
Joined: 05 January 2006

It is impressing, how SSTS techniques and nested eliminations can shorten the solutions (but of course the steps would be much harder to find without the help of programs). The best my program found so far are 16 steps for this puzzle.
[Added:] On the other hand i count at least 15 elimination chains in this solution also ...
ravel

Posts: 998
Joined: 21 February 2006

With the ultra ultra hard being posted on the hardest thread.......There should be some puzzles that would test SSTS to the max.......The hardest which you can trace with SE is my latest Fluid Drive #8 ....... I have also posted another nasty one but as it wasn't a pearl, I couldn't name it the Fluid drive ....... modified it a bit & called it "Gyroscope #1" it should be tackled by you ... however one chain at least should have multiple colouring according to gsf's rating.........

tarek

tarek

Posts: 2699
Joined: 05 January 2006

### Solving other puzzles

.
Tarek, to answer one of your questions: I have no qualms about using uniqueness, if I spot the chance. (I don't see any point in proving a given, and uniqueness is a given.)

I've just solved Ocean's "The Anemone", on another new thread, and maybe I should also try one of ArtoI's incredible puzzles.

But nothing motivates me more to solve any puzzle than the wish of the composer that I do so. So soon I will do the puzzles you suggest.
gurth

Posts: 358
Joined: 11 February 2006
Location: Cape Town, South Africa