The New Sudoku Players' Forum

[ravel]

I don't see any riddle.

No riddle, when you write

[r5c6]=4=[r9c6](-4-[r9c2])-4-[r9c8]=4=[r7c8]-4-[r179c2]-2,3,8-[r3c2]
(-1-[r39c9]-3-[r4c9])-1-[r3c8](-3-[r456c8]=3=[r4c7])-3-[r9c8]-7-
-[r456c8])=7=[r4c7],

and so r5c6=4 which solves the puzzle.

Then we can immediately see, that (reading the chain from left to right) r5c6<>4 both leads to r4c7=3 and r4c7=7, a contradiction.

But looking at the beginning and the end of the chain one only can see that either r5c6=4 or r4c7=7 and is asking oneself, why this implies that r9c6<>4 (we saw a similar solution by you leaving an open either/or problem, which was harder to solve than the puzzle).

So the riddle is, why you like to present solutions in a way, that is harder to understand than necessary.

[udosuk]

Yep, I have to agree on the views of ravel & ronk (R & R?) here...

For example, from this solution Carcul posted, I had absolutely no clue how he could make those pre-conditions, but he just stated them in a "this is baby stuff" style... Way cool!

Speaking of riddles, Carcul seems to enjoy posting riddles & exercises and leaving us baffled for the rest of our lives ... He didn't even bother to follow on this thread at all... Must be thinking all of us have solved it... Well anyone?

[Carcul]

No riddle, when you write...

Sometimes all is needed is a more carefull looking.

we saw a similar solution by you leaving an open either/or problem, which was harder to solve than the puzzle

Thank you.

but he just stated them in a "this is baby stuff" style...

I like that expression.

Speaking of riddles, Carcul seems to enjoy posting riddles & exercises and leaving us baffled for the rest of our lives

That's true: I like to make riddles and very hard problems, I do like to make people think, but not for the rest of their lives. But I know I am not very good at making Sudoku Riddles. Perhaps someone could write some reasonable properties of a good riddle. Or perhaps I am just not using the correct words.
However, in the case there is someone out there interested, I also have some very hard problems about organic chemistry.

Regarding the Exercise, the only thing I can do is to post my solution.

Carcul

[tarek]

here is a machine analysis of "292: Tarek #1/1 (9.9)"

Code: Select all

Hidden Double
Finned Swordfish
Finned Swordfish
Finned Swordfish
Simple Guess
Simple Guess
Box-line interaction
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Box-line interaction
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Simple Guess
Complex Guess
Simple Guess
Simple Guess
Naked Double
Simple Guess
Simple Guess
Level 3 FC
Simple Guess
Box-line interaction
Naked Triple
Level 3 FC
r3c2------1
r5c3------2
ALS-XY (10 Cells)
Level 3 FC
r7c3------3
Box-line interaction
Level 2 FC
Level 3 FC
r7c9------4
r2c7------5
Finned Swordfish
ALS-XY (7 Cells)
r2c1------6
r1c2------7
r5c1------8
r2c8------9
r4c1------10
r1c5------11
Box-line interaction
Hidden Double
Hidden Triple
Finned XWing
r7c5------12
.
.

Non single steps: 48
Advanced steps: 38
Difficulty Index: 0.79
Guesses: 26
Guessing Index: 0.68
Singles Tail: 48

Placemnts are numbered until the singles tail
Single eliminations, hidden singles removed

with 26 guesses, this is hardly a good solution......Somebody out there hopefully can supply a better one

tarek

[Eioru]

Code: Select all

 . . * | . . * | . . .
 . * . | . * . | . . .
 * . . | * . . | . . .
-------+-------+-------
 . . * | . . * | . . *
 . * . | . * . | . * .
 * . . | * . . | * . .
-------+-------+-------
 . . . | . . * | . . *
 . . . | . * . | . * .
 . . . | * . . | * . .


I suspect that the results would be disappointing because of the limited clue numbers (21 max).......

tarek

I can't find anyone during two days' searching~

[tarek]

I can't find anyone during two days' searching~

I agree that the problem with this pattern is generating a valid puzzle in ht efirst place...........

I managed just a few (<20).......This is not sufficient to screen for a very hard one....The hardest of these was (SE9.1,gsfr99344):

Code: Select all

 . . 6 | . . 9 | . . . 
 . 4 . | . 3 . | . . . 
 5 . . | 1 . . | . . . 
-------+-------+------
 . . 2 | . . 6 | . . 3 
 . 3 . | . 9 . | . 5 . 
 1 . . | 5 . . | 8 . . 
-------+-------+------
 . . . | . . 1 | . . 6 
 . . . | . 4 . | . 9 . 
 . . . | 8 . . | 2 . .

tarek

[ravel]

with 26 guesses, this is hardly a good solution......Somebody out there hopefully can supply a better one

From the jewellery thread:

Under SSTS, r1c3 & r5c7 are the only backdoor cells (both require multiple colors) ...

So 1 guess and multi-colors solve it.

.....This is not sufficient to screen for a very hard one....

Hard enough fo my list - 5 steps.

[Eioru]

Code: Select all

*..*..*..
.*..*..*.
..*..*..*
*..*..*..
.*..*..*.
..*..*..*
*..*..*..
.*..*..*.
..*..*..*

This is original puzzle,
and I want try to empty 3 units ( row, column, box )

like this

Code: Select all

*..*..*..
.*.....*.
..*..*..*
*.....*..
.........
..*.....*
*..*..*..
.*.....*.
..*..*..*

[tarek]

and I want try to empty 3 units ( row, column, box )

like this

Code: Select all

*..*..*..
.*.....*.
..*..*..*
*.....*..
.........
..*.....*
*..*..*..
.*.....*.
..*..*..*

I suspect that it would be very difficult....you've got 20 clues only there........with an empty box I achieved 21 clues....
good luck

tarek

[RW]

Not aiming for any records here, other than perhaps my personal best. Found some toughies in my search for 21s in the Pt-grid, guess it's my duty to report them here:

Code: Select all

1.......9..7.8...6...3...5.....4.8..7....1....96........82.....5......63.6..7.4..
1.......9.5....3......27..4....4.8..7....1....96...5..3...........9.8.6...257....
1.....78....1.9.......2...4....4.8..7....1.3...6........8.6...5..4...2..9....3.1.
1...56.........32...9.....4...6...9.7....1...8...3.5..31.........49...6.....7...8
1...56.8.......32...9.....4...6...9.7....1...8...3.5..3..........49...6.....7...8
12....7.......9...6..3...5...1.4.8..7.....6...9......1...2...7.5.4.1...3.....3...
12....7......89......3....4..1.4....7.....6...9...25........97...4.1...3.6.5.....

None are diagonal, none are symmetrical, no gems, only ugly gray rocks.

RW

[daj95376]

ravel, A quick-'n-dirty preliminary test just occurred to me that you may wish to consider trying before doing a full step count on a puzzle. It might prove to be informative.

* Perform an SSTS reduction on the puzzle. (Or any basic reduction.)
* Perform a single step on the puzzle.
* Count the number of candidates remaining.

[ravel]

Daj,

i am not sure what you mean. As i understand it, what you describe is just what i am doing (but my basics dont include xy-wing, swordfish and coloring):
I perform a single step for all candidates, that can be eliminated, then apply basics and count the remaining candidates. Under those with the minimum of remaining candidates i select one (by puzzle order or randomly) for the next step.
This process is done starting with each of the candidates that can be eliminated after first getting stuck with the basics.

Thanks for the puzzles, RW, will check them on Monday.

[Viggo]

Code: Select all

1.......9..7.8...6...3...5.....4.8..7....1....96........82.....5......63.6..7.4..
1.......9.5....3......27..4....4.8..7....1....96...5..3...........9.8.6...257....
1.....78....1.9.......2...4....4.8..7....1.3...6........8.6...5..4...2..9....3.1.
1...56.........32...9.....4...6...9.7....1...8...3.5..31.........49...6.....7...8
1...56.8.......32...9.....4...6...9.7....1...8...3.5..3..........49...6.....7...8
12....7.......9...6..3...5...1.4.8..7.....6...9......1...2...7.5.4.1...3.....3...
12....7......89......3....4..1.4....7.....6...9...25........97...4.1...3.6.5.....

RW

Hi RW

I checked you puzzles with the Sudoku Explainer. The ratings are:

9.0
9.1
9.2
9.1
9.0
9.1
9.1

/Viggo

[daj95376]

ravel, I don't think my suggestion will work with your solver because it (possibly) doesn't contain enough of the techniques necessary to support the first bullet below. Here's an example of what I'm suggesting.

* Perform all non-chaining techniques until you can't proceed any further; e.g., N-tuples, Locked Candidates, X-Wing, Swordfish, Jellyfish, XY-Wing, XYZ-Wing, BUGs, and URs. Coloring and Multiple Coloring can be included as exception techniques here.

* Perform, once, all chaining technique eliminations possible with your solver; e.g. XY-Chain, Forcing Chains/Nets, and elimination-by-contradiction.

* Count the number of candidates remaining and use this as a rough estimate on the puzzle's difficulty.

[ravel]

Ah, i see now, what you mean.
It reminds me on gsf's batch moves.
The disadvantage i see is, that if you would only need one (maybe small) contradiction chain to make another one possible, which finally solves the puzzle, then this puzzle might be overrated. On the other side, if you really need almost all of the possible eliminations in one move to get to the solution, it would be underrated.

The main advantage is, that it can be calculated much faster.

I think, the main difference between gsf's and my rating is - roughly speaking - that he is performoning a breadth first search for candidate elimination and counts all of them as one step, whereas i try to minimize the number of depth first found eliminations and count each as a step.