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 Very difficult puzzle (?) 
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Posted on: Thu Jun 07, 2012 10:35 pm




Posts: 246
Location: Lisbon, Portugal
Joined: Sun Sep 18, 2011 5:40 pm
Post Very difficult puzzle (?)
What's up today? At 21H30M GMT only 4 players ( in Europe ) have gained the Golden Star of the day.
Is it because the 6x6 difficult?

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Posted on: Fri Jun 08, 2012 6:16 am




Posts: 422
Location: Canada
Joined: Fri May 13, 2011 2:43 am
Post Re: Very difficult puzzle (?)
I don't know about everyone else but I was busy this evening until now...


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Posted on: Fri Jun 08, 2012 7:41 am




Posts: 73
Location: Delft, The Netherlands
Joined: Fri May 13, 2011 7:15 am
Post Re: Very difficult puzzle (?)
I couldn't solve the 8x8 difficult, 9x9 difficult and 12x12 difficult (which is why clm succeeded in stealing my first place :/).


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Posted on: Fri Jun 08, 2012 9:02 am




Posts: 694
Joined: Fri May 13, 2011 6:51 pm
Post Re: Very difficult puzzle (?)
sheldolina wrote:
I couldn't solve the 8x8 difficult, 9x9 difficult and 12x12 difficult (which is why clm succeeded in stealing my first place :/).


My purpose was not stealing your place, apologize, just to borrow it for a while [biggrin] [biggrin]. Among the yesterday's puzzles, I think the 8x8 difficult was the more complex. In the 9x9 and 12x12 you probably lost some of the combinations in the multip cages, otherwise I do not understand why you failed in the solution. And I am sure that (after the exams?) you will recover the first place. Good luck in the exams (for you and your daddy [thumbup]).


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Posted on: Fri Jun 08, 2012 9:19 am




Posts: 31
Joined: Mon Mar 05, 2012 12:45 pm
Post Re: Very difficult puzzle (?)
Confirm, yesterday I was busy most of the day and in the end did not manage the 8x8 difficult - if only I had a few minutes more... It required quite a few hypotheses to solve it, and I checked the correct one as last [sad]


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Posted on: Fri Jun 08, 2012 12:49 pm




Posts: 246
Location: Lisbon, Portugal
Joined: Sun Sep 18, 2011 5:40 pm
Post Re: Very difficult puzzle (?)
sneaklyfox wrote:
I don't know about everyone else but I was busy this evening until now...


It's natural with you because you take care of your little Daniel and he must give much work.

sheldolina wrote:
I couldn't solve the 8x8 difficult, 9x9 difficult and 12x12 difficult (which is why clm succeeded in stealing my first place :/).


After completing your exams you must train to do more the regular puzzles to acquire the title of " The most complete player of Calcudoku ". Maybe Patrick will create this " honorific title "!



Anyway I think yesterday was the day with less golden stars. Maybe Patrick confirms this. And, in my opinion, it was not because any 8x8, 9x9 or 12x12, but because the difficult 6x6.

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Posted on: Fri Jun 08, 2012 1:36 pm




Posts: 220
Joined: Fri Jun 17, 2011 8:15 pm
Post Re: Very difficult puzzle (?)
The 6x6 started slowly with a lot of empty squares around the parameter - just the 1 in e1 was obvious, if I remember correctly. But a little perseverance and it fell into place. Did it hinge on whether the 9+ in the d2e2 was 4,5 or 3,6. I don't remember now, but a few things like - eliminate a choice over here, eliminate another over there - and it came together.

I agree with clm, that the 8x8 was the most difficult puzzle of the day. I had to put that puzzle away and come back to it twice before I got the solution. And that meant that I almost finished the day as jotempe did - I submitted my solution with much less than an hour to spare, maybe less than 15 minutes. The 8x8 was a real stumper for me.

I didn't finish the 12x12 until today though, so no gold star for me.


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Posted on: Fri Jun 08, 2012 3:48 pm




Posts: 246
Location: Lisbon, Portugal
Joined: Sun Sep 18, 2011 5:40 pm
Post Re: Very difficult puzzle (?)
Jaek : You are right and I am right, the difficulty of a puzzle is ( also ) a subjective one. Perhaps I was more lucky with the 8x8 than other times. I would like that anyone who wants classifies the difficult puzzles 6x6, 8x8, 9x9, 10x10 and 12x12 with a factor from, e.g., 1 to 5 and the next day Patrick would present their average as comparation with the official classification. That would be interesting to see how people found more or less difficult the puzzles.

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Posted on: Fri Jun 08, 2012 8:22 pm




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Post Re: Very difficult puzzle (?)
sheldolina wrote:
I couldn't solve the ... 9x9 difficult ...


With respect to the yesterdays’s 9x9 puzzle, I was thinking in your comment and thought that the following notes could be useful to see that this calcudoku is, in fact, quite easy, if we apply the analysis, the basic rules.

Image

Green: The 5 of row 9 (in this case with a 2) to g8. Then “24x” = [1,4,6] >>> a8 = 1, a9 = 7 (unique).

Purple: “18144x” = [4,7,8,9,9], [6,6,7,8,9] so it does not contain a 3 >>> e9 = 3, h9 = 9.
The 9 of column i to i9 (unique) so we are left with [4,7,8] for this cage.
Addition rule to columns h and i: “84x” (+) + h7 + h8 = 30. Since “84x” = [1,2,6,7] (16) or [1,3,4,7] (15) (obviously [2,2,3,7] not considered due to a double 2 and there is a 2 in “10x”) >>> h7 + h8 = 14 or 15, neither can be done including a 4, so g8 = 4, h7-h8 = [7,8] and then “84x” = [1,3,4,7].

Brown: The 9 of column e to e7 >>> d7 = 7.
Addition rule to rows 3 and 4: a + b + c (cells d3, e4, h4, respectively) = 12 but a and b are even so c is even, so c = h4 = 2, h5 = 5. Now a + b = 10 but [1,9], [3,7], [4,6] or [5,5] are invalid thus [2,8] >>> d3 = 2, e4 = 8. Additionally “13+” = [4,9] (unique) >>> c2 = 4, d2 = 8.

Light blue: First b9 = 4, c9 = 1, d9 = 6.
Now looking to the pair e8-f8 (sum of 11), since [2,9], [3,8], [4,7] are not valid >>> e8 = 6, f8 = 5, e1-e2 = [1,2] >>> f1-f2 = [6,8].
Also the 9 of column c to c3 >>> b3 = 5.
Addition rule to columns f and g: g1 + g2 = 12 = [3,9].

Red: Directly c8 = 2 (unique for this cell). Now c1 cann’t be a 5 (a 4 and a 6 in column d) so c7 = 5, c1 = 6 (or, inversely, c7 cann’t be a 6 due to g8 = 4, d2 = 8 that would make imposible the cage “0-”). As a consequence, d8 = 3, d1 = 5.
Addition rule to rows 7, 8 and 9 (sum of 135): g7 + i7 = 3 >>> g7 = 2, i7 = 1.
Addition rule to rows 5 and 6: a6 + b6 = 3 >>> a6 = 2, b6 = 1. Now “5-” = [2,7] ([3,8] is not possible due to two 8’s in rows 1 and 2).
Addition rule to columns a and b: a1 + a2 = 14 >>> [5,9] with a1 = 9, a2 = 5.

The rest can be quickly finished (not represented in the graphic): The 5 of column i to i4 (unique) >>> i3 = 4; now h1-h2 = [1,4] and i1-i2 = [3,7]. Other: d6 = 4, d5 = 9. Also c5 = 8, c6 = 7. And, i.e., the 6 of column i to i6, or, f2 = 6, f1 = 8, etc. …

(The official solution because in the future will not be available [biggrin]:)

Image


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Posted on: Fri Jun 08, 2012 9:12 pm




Posts: 220
Joined: Fri Jun 17, 2011 8:15 pm
Post Re: Very difficult puzzle (?)
clm wrote:
Green: The 5 of row 9 (in this case with a 2) to g8. Then “24x” = [1,4,6] >>> a8 = 1, a9 = 7 (unique).

CLM's solutions are a pleasure to see. I stumble through many of these same processes but don't think to note them as I proceed and certainly don't come back around to write the solutions up so well. So thanks, as always, for sharing.

I want to point out something in case someone trying to follow his logic gets flustered at first. When clm writes "(unique)" that means that some thing or things in the relevant row and/or column force a single option for that cell. In the case of:
"a8 = 1, a9 = 7 (unique)",

this is short hand for:
"Because of the known values in row 9, a9 must be 3,9, or 7. A5 = 3 so a9 <> 3. But in addition, a8a9 is 7- so if a9 = 9 then a8 = 3. Again that doesn't work. So it must be that a9 = 7 and a8 = 1."

I'm only pointing this out because I'd hate for someone to read the first section and then be stumped as to how the 1,7 combo was arrived at. Just look at the row and or column and see why other options are invalid. And then note how useful the addition rule, parity, etc. are for solving puzzles analytically and try them out the next time you are stuck on a puzzle.


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