29

Your puzzle is probably harder than you think it is. This is just a heuristic answer. Some puzzles turn out easier than the writer expects. But in my experience, it's much more common error to make a puzzle that's harder than you intend. When judging the difficulty of your own puzzle, it's easy to forget that you have the advantage of knowing the answer. ...


14

One way is to use a hash function with a very small output space. E.g. if it's a number, give the sum of the digits modulo 5. That way it's not much use in filtering down a search space of thousands, but it does give a quick-reject for the majority of incorrect keys. If you want, you could even guess at possible errors that people will make and try to find a ...


13

Modern sudoku puzzles are ranked according to the difficulty of the techniques required to generate a solution. It's important to note that there is no standardized system or metric, but rather, these are based on qualitative assessments. playr.co.uk lists these requirements for its various ratings: Level 1 puzzles can be solved simply by reducing the ...


8

In my experience, it's generally What is the hardest technique required to solve it. Example hardest: Single Position - Easy puzzle Ex. Candidate Line - Medium Puzzle Ex. Naked Pair - Hard Puzzle Ex. Swordfish - Very Hard Puzzle Ex. Forcing Chains - Master Puzzle Definitions can be found here: http://www.sudokuoftheday.com/pages/techniques-overview.php


8

Lights Out puzzles have a polynomial time algorithm by linear algebra. "Draw this shape without picking up your pencil" puzzles have a polytime algorithm which follows from the proof of which graphs have Eulerian circuits. Sliding puzzles like the 15-puzzle are easy (though hard to solve in a minimal number of moves). IMO these examples kind of prove your ...


8

I suspect the complexity class is not too important. In the example of Sudoku, the NP-complete problem is "given a partially filled in $n \times n$ grid, state whether it can be completed to a legal arrangement". The popular puzzle is "given a partially filled in $9 \times 9 $ grid that is known to have a unique solution, find that solution". In the ...


7

3 different approaches: I think, whenever possible, the cross-checks of partial solutions should be fun in themselves. Of course it depends a lot of the nature of the result (a value? a phrase? something more abstract?), but instead of using some encryption, I would rather build a mini-puzzle around the solution. Something which is not very demanding, but ...


7

I don't think there's any hard-and-fast way to rank the boards, but here are a few thoughts. Let $z = $ the number of zombies. Let $g = $ the number of ghosts. Let $v = $ the number of vampires. Let $n = $ the size of the board ($n=4$ indicates a 4 $\times$ 4 board). Let $s = $ the sum of all the numbers around the edges of the board. Let $m = $ the number ...


7

I think the problem with trying to rate these with one number is that most of the most popular brainteasers present challenges on up to three different "challenge spectrums": Some are highly dependent on actual skills, knowledge or tools, like ones that can't easily be solved without a spreadsheet, or that are incredibly hard without knowledge of ...


7

The best way to run difficulty tests on your puzzle is the tried-and-true method of a test audience. As others have pointed out, do not include yourself in this audience - you are biased because you already know the solution. You can try to be rigorous in your testing b getting a large sample audience to test your puzzle against, which is the usual ...


6

The critical factor is the connectivity of the graph. The Hamiltonian path problem is known to be NP-complete. Years ago I saw charts from a talk called "Where are all the hard problems?" (seems no longer available) The point was that although Hamiltonian path is NP-complete, specific instances are easy. Either (for high connectivity) you find a path ...


5

The interesting thing about anagrams is how their difficulty increases rapidly with the insertion of even a single new letter. For example, a short anagram like WROC can be solved within a glance. This is because of the number of ways of ordering the letters is the factorial of the number of letters: there are $4!=4*3*2*1=24$ possibilities to order the four ...


5

You didn't say what kind of puzzles you were asking about. I enjoy programs that generate logic puzzles. I suspect for those, the programmer writes a solver with whatever logic s/he thinks the person solving should use. The program then generates a solution and feeds the (empty set) of clues to the solver. If the solver fails, you add a clue and try ...


5

I think this is very hard question to answer practically. So even though I do not have an direct answer to it I would like to share my experience, which in related area. I am living on a Russian site, that provides unique puzzles for people to solve. Here is the facts about how hard is to estimate puzzle hardness for us: It has about 400 selected puzzles ...


4

I believe the best way to judge puzzlers would be to have a round of beta testing. Create a small group composed of your colleagues, friends and family, making sure that you include people of all skill levels. Include your not-so-tech-savvy parents, your pretty-but-not-very-bright neighbour, your quick-thinking colleague and people from all walks of life ...


3

As mgkrebbs stated, the most widely known system for ranking the difficulty of crossword puzzles is by the day of the week. The New York Times is famous for doing this, with many other crosswords following in its footsteps. Monday is the easiest and Saturday is the hardest, with Sunday puzzles being larger and having the difficulty of about a Thursday ...


3

Image captchas are currently the most brute-force resistant means of asking or confirming information. One could use images to depict a short message. You could also ask the decoder to take the first character of the names of each of the images. For more clarity, you could use a limited dictionary of about 1000 words or so. As long as you use a different ...


3

Here are three sites where you can find very difficult puzzles: https://www.themissingdocs.net/bridge/LoopDeLoopBridge.html https://www.kakuro-online.com/slitherlink/ kwontomloop.com If you want to start with the most difficult, try an "Unlimited" at the first site.


3

http://www.janko.at/Raetsel/Slitherlink/index.htm got some puzzles up to 45x31. You can sort them by size (Größe) or difficulty (Schwierigkeitsgrad). http://www.nikoli.com/en/puzzles/slitherlink/ got some hard ones, but only a few free samples. https://www.chiark.greenend.org.uk/~sgtatham/puzzles/js/loopy.html can generate puzzles of any size, limited only ...


3

I would say that riddle difficulty is hard to rate. Some people will find one riddle easy, while another person will find it hard. It all depends how you approach the solution. Some riddles involve little-known facts, and therefore are difficult to solve.


3

On the popular British TV gameshow, "Pointless", they often have a round that has a category and then a series of the words that fit that category in anagram form (presented as English words). In this case the anagrams are of varying difficulty, but with the presence of the given category, this gives clues to the players. The way I tend to attempt them is to ...


2

Ask a bunch of people this riddle. Then, rate the difficulty depending on how many people you ask before someone gets it. If it takes 6 people, rate the difficulty 6.


2

One approach would be doing a breadth-first brute force and noting the highest depth level visited before arriving at a solution. The higher the needed depth, the more difficult the puzzle is.


2

I got in touch with the the owner of the puzzle page and here is his reply: " I had to look this up myself in the source code (Undead was submitted by another developer, not written by me). Apparently the effects of the difficulty level setting are: constrain the maximum length of a line of sight. At easier difficulty levels, the game avoids really long ...


2

I think the solution is using a set of characters or figures that are unknown to the typical brute-force dictionary. Take a look at this question: Can you decipher the hidden message in this Christmas card image? Hopefully this helps.


2

If it's not possible to solve with the other symbol, then you are basically doing the precise inverse of guess&check, which means that it will have a unique solution, since the other remaining symbols give enough information to guarantee that symbol that you have removed, so it does not remove required information. Does that explanation make sense?


2

This website has the hardest slitherlinks that I know of: http://kwontomloop.com/puzzle.php Also, as mentioned in the comments by Eric, https://www.gmpuzzles.com/blog/category/loop/slitherlink/ has really good slitherlinks


1

Your logic is correct. The resulting puzzle can indeed be solved in a relatively straightforward way as you described. Given this, Of course, this doesn't prove that it always works, but the logic is good and this example works.


1

If you use a Sudoku solver, for example SudokuWiki.org, you can add up the number of times the solver uses a particular method, so: 1pt: Hidden Singles 2pt: Naked Pairs/Triples 3pt: Hidden Pairs/Triples ... 7pt: X-Wing ...etc. Add them all up and this gives you a difficulty level.


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