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Using the fact that each puzzle has a unique solution as a clue
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svdb



Joined: 15/03/2008 22:07:11
Messages: 43
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Sometimes, in a puzzle, you know that if a certain step would yield a solution, then there must be another solution. As each puzzle is supposed to have a single unique solution, you know that that step must be wrong.

I personally tend not to use this information, as it feels like cheating, because I would be using meta-information which I don't consider to be part of the puzzle.

How do others think about this? Is using the fact that each puzzle has a unique solution cheating, or do you consider it to be just another clue?
connect4


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Joined: 04/03/2008 05:04:39
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For me, it depends on the puzzle. Sudoku and the other number puzzles are ones will I won't do that (unless I'm in a timed competition, in which case anything goes!). In archipelago, on the other hand, I use it regularly (and it's probably one of the only ways for me to do them).

I agree that it feels dirty to make that assumption, but in some puzzles I don't have better tools (which reminds me, I had meant to make a "tips/tricks for genre XXX and YYY" thread at some point, as some of those genres just throw me for a loop!)
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Bram



Joined: 04/03/2008 13:59:34
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Yeah i agree, it depends on the puzzle genre. One of the most famous ones for me are Dominoes puzzles(which aren't on this site). There uniqueness is prob the step i use most.
It also depends if i solve the puzzle for fun or speed. In competitions i use uniqueness when i can, because you just want to finish it as fast as possible. When i do it for fun, i try to avoid using a uniqueness assumption, just to have that extra bit where you also see the puzzle is unique and not just assume it is.

(on a side note, i like XXX, but YYY tend to be a bit harder )
Johan


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Joined: 22/12/2006 20:08:51
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I, for one, don't feel any remorse when I use the uniqueness property in solving, and always consider it part of the game (that is, unless I need to check a puzzle for correctness).
achan1058


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Joined: 19/04/2008 05:22:28
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Personally, I use uniqueness as a second last resort. The very last resort being guessing and checking whether a guess leads to a contradiction (ie. use of colours). However, for some puzzles, I needed to use both a lot......
mathgrant


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Joined: 19/08/2008 20:52:44
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I, for one, refrain from using such metalogic. I want to appreciate the logical solving process that the author intended. It is this process, and not simply reaching the final solution, that matters most to me. I don't want to merely think, "Buhhh, I'm smart because I solved this puzzle!", but also, "Wow, this author crafted a beautiful puzzle." The solving process is half of the beauty. That's my philosophy.

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achan1058


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Joined: 19/04/2008 05:22:28
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It would be interesting, if someone designs a puzzle that uses unique solution as the main key for solving it. Can it be done, I wonder?
connect4


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Joined: 04/03/2008 05:04:39
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achan1058 wrote:
It would be interesting, if someone designs a puzzle that uses unique solution as the main key for solving it. Can it be done, I wonder? 


If you look at the 2007 US Sudoku Championship final puzzle in the advanced category, Thomas Fisher used that as the breakthrough he needed to solve one of the puzzles. You technically could have gotten away with using Y-wings to solve it, apparently, but it was significantly easier if you use uniqueness.
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Shvegait



Joined: 13/02/2010 03:36:12
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achan1058 wrote:
It would be interesting, if someone designs a puzzle that uses unique solution as the main key for solving it. Can it be done, I wonder? 


I realize these posts were from two years ago, but I've been thinking about this a bit recently.

Generally I dislike assuming uniqueness as a clue, but I'll use it if it comes up. I consider it to be just a weakness in the puzzle, especially if such opportunities arise frequently. It seems to me that in some genres the situation arises rarely and barely helps when it does (Nikoli Fillomino puzzles come to mind), but in others, it's all over the place.

There is a genre on this site now (it wasn't on the site two years ago) that is extremely vulnerable to using uniqueness as a clue for solving. Every puzzle in the genre becomes easier to solve and some even become trivial (unfortunately). Tweaking the rules a little bit could solve that weakness, but it would probably create other issues. If you've done enough puzzles from the genre, you probably know which one I'm referring to, but I don't want to spoil it for anyone.
fl0rrat



Joined: 10/10/2010 20:04:05
Messages: 237
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I also don't want to use the fact that a solution is unique to solve the puzzle. In puzzle where I assume something, and then it turns out that the assumption was true and I solved the puzzle, I usually go back and assume the negation, to show that will lead to a contradiction. The genre honey islands is one of the few exceptions for me, since I think it's hell to prove uniqueness for a particular puzzle.

achan1058 wrote:
It would be interesting, if someone designs a puzzle that uses unique solution as the main key for solving it. Can it be done, I wonder? 

Do you mean a puzzle where you need to use the fact that the puzzle has a unique solution to solve the puzzle? Or a puzzle where using that fact is just very useful? The first case can't be done: if a puzzle has a unique solution, you can always show that without using that fact (so if you want to design such a puzzle, it has to have multiple solutions XD). The second case is very common.
 
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