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Why symmetry?

 
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nobodyimportant

Joined: 01 Nov 2008
Posts: 1
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PostPosted: Sun Nov 02, 2008 4:24 am    Post subject: Why symmetry? Reply with quote

Hello all,

I just finished coding my sudoku app (using actionscript in flash) and it works decently well (could be better, but I'm not exactly a programmer). I was reading around this forum and came across the symmetry poll and I thought to myself that symmetry puzzles don't look very attractive.

I wanted to know what the supposed benefits are from using puzzles that are symmetrical, right now mine are diagonally symmetrical because I changed it to be so (previously I had it removing a cell in the top half, then removing a random cell in the bottom half).

If I don't use symmetry, is it considered more risky that a puzzle will be unsolvable?

And by the way, are you all comp. sci majors or something? I go to an art school and when I was reading this forum I only understand one out of every ten terms you guys stated Very Happy or did you learn somewhere else? Anyways the only reason I ask is because I'm currently in art school for web design, but this has led me into an interest in web development, and further, into an interest in programming. But since I'm about to graduate it's a little bit late to rethink majors Razz.

Thanks for any responses!
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garthd

Joined: 29 Apr 2006
Posts: 32
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PostPosted: Sun Nov 02, 2008 12:28 pm    Post subject: Why symmetry Reply with quote

Various types of symmetry are possible - but as far as I know, to use this or not comes down to personal preference. Many people find symmetry more aesthetically pleasing, and so many newspapers have puzzles with symmetry.

Quote:
If I don't use symmetry, is it considered more risky that a puzzle will be unsolvable?


Symmetry (or lack of it) will not affect the difficulty or solvability of the puzzle. You need some kind of backtracking method to check a puzzle only has one valid solution (otherwise its strictly not a valid puzzle). If you aren't worried about multiple solutions, a simple check ot ensure particular numbers/clues aren't repeated in a row, column or subgrid should ensure you can solve the puzzle.
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klarax

Joined: 07 Dec 2008
Posts: 2
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PostPosted: Sun Dec 07, 2008 1:53 am    Post subject: Reply with quote

on a further note:
if you create a board with symmetry. by rotating that board, or flipping it. will result in another valid generated board
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m_b_metcalf

Joined: 13 Mar 2006
Posts: 210
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Location: Berlin

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PostPosted: Sun Dec 07, 2008 10:40 am    Post subject: Reply with quote

klarax wrote:
on a further note:
if you create a board with symmetry. by rotating that board, or flipping it, will result in another valid generated board

Only superficially: the two puzzles will be isomorphs of one another, see this.

Regards,

Mike Metcalf
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Adak

Joined: 27 Feb 2008
Posts: 87
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PostPosted: Sun Dec 07, 2008 11:40 am    Post subject: Reply with quote

@nobody:

I'm not a hobby programmer myself, but what snowed me was not the programming terms, but all the detailed "Sudoku speak", on this forum.

I had to go look up "Canonical", because the only Canons I knew about were the one's from the Church. Smile

You need it these detailed expressions to be precise and short, but it's a handful to wrap your head around if you've never been exposed to it.
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