'When a Newspaper Publishes an Unsolvable Puzzle' (10zenmonkeys.com) 23
Slashdot reader DevNull127 writes: It's a newspaper puzzle that's like Sudoku, except it's impossible. [Sort of...] They call it "The Challenger" puzzle — but when the newspaper leaves out a crucial instruction, you can end up searching forever for a unique solution which doesn't exist!
"If you're thinking 'This could be a 9 or an 8....' — you're right!" complains Lou Cabron. "Everyone's a winner today! Just start scribbling in numbers! And you'd be a fool to try to keep narrowing them down by, say, using your math and logic skills. A fool like me..." (Albeit a fool who once solved a Sudoku puzzle entirely in his head.) But two hours of frustration later — and one night of bad dreams — he's stumbled onto the web page of Dr. Robert J. Lopez, an emeritus math professor in Indiana, who's calculated that in fact Challenger puzzles can have up to 190 solutions... and there's more than one solution for more than 97% of them!
At the end of the day, it becomes an appreciation for the local newspaper, and the puzzles they run next to the funnies. But with a friendly reminder "that they ought to honor and respect that love — by always providing the complete instructions."
"If you're thinking 'This could be a 9 or an 8....' — you're right!" complains Lou Cabron. "Everyone's a winner today! Just start scribbling in numbers! And you'd be a fool to try to keep narrowing them down by, say, using your math and logic skills. A fool like me..." (Albeit a fool who once solved a Sudoku puzzle entirely in his head.) But two hours of frustration later — and one night of bad dreams — he's stumbled onto the web page of Dr. Robert J. Lopez, an emeritus math professor in Indiana, who's calculated that in fact Challenger puzzles can have up to 190 solutions... and there's more than one solution for more than 97% of them!
At the end of the day, it becomes an appreciation for the local newspaper, and the puzzles they run next to the funnies. But with a friendly reminder "that they ought to honor and respect that love — by always providing the complete instructions."
Multiple solutions does not make it unsolvable (Score:5, Insightful)
It just means you get to choose a solution.
Re: Multiple solutions does not make it unsolvable (Score:3)
Right. Wtf... how is lacking a singular solution mean it's unsolvable. When did the concept of solution become so myopic.
Btw, I did not see that coming...
Re: (Score:2)
It's in the word "solution"
If you've ever tried a sudoku with multiple solutions, unless it specifically says multiple solutions might be possible, it's badly-designed. I don't know whether it's in the spec, but as far as I'm concerned, a sudoku or other number puzzle should have a singular solution that you can figure out logically.
Re: (Score:3)
The instant the player is forced to guess in a Sudoku, it stops being a puzzle. If you can't solve it logically, it's unsolvable as a puzzle.
It's like a crossword with no clues. You could brute-force a "solution", sure, but it doesn't make sense to call it a 'puzzle' at that point as the puzzle part has been removed.
Re: (Score:3)
> If you can't solve it logically, it's unsolvable as a puzzle.
Huh? What does the word unsolvable mean?
NO solution.
if there ARE solutions then it is solvable. It doesn't matter HOW you come to the solution.
Re: (Score:2)
This isn't that difficult. Try reading my post again.
Re: (Score:2)
What part of the definition of puzzle [merriam-webster.com] do you not understand?
If you have to resort to guessing that doesn't change the fact that it a puzzle. Guessing isn't fun -- but you STILL have puzzle. You are conflating a bad puzzle with no puzzle.
If a puzzle has multiple solutions that doesn't make in "unsolvable" -- probably just "not interesting", "bad", "not fun", etc.
Re: (Score:2)
I strongly disagree with that absurd definition. Guessing and puzzling are nothing alike. Randomly turning a Rubik's cube is not the same as solving one.
Introducing guessing changes the nature of the activity so much that it's wrong to even call it a Sudoku puzzle.
Maybe you don't know what a solution is? The solution to a 15 puzzle is the sequence of moves necessary to move from the initial scrambled state to a completed state, not the final state itself. I thought this was obvious. If you were strugg
Re: (Score:3, Informative)
The title to the article is very misleading.. I read it trying to see why it was unsolvable and yet they gave a solution.
The title should read, "Overly pedantic man ensures self-inflicted torture while failing to find a single solution to a puzzle with multiple solutions"
So much for his logical mind (Score:2)
He managed to produce multiple solutions for the puzzle, within the specified rules, but failed to work out that meant there were multiple possible solutions!
I appreciate the publishing of a single answer to the puzzle in the paper wasn't helpful, but that should have been the clue to think about the wider problem a bit more.
Re: (Score:2)
What are they teaching instead of basic algebra? (Score:2)
Re: (Score:3)
Not necessarily. There is also the constraint that the numbers are between 1 and 9.
Re:What are they teaching instead of basic algebra (Score:4, Informative)
I wrote a small program to find all solutions. If I did not make any mistake in my program the problem in the newspaper one has exactly 46 solutions.
However, after changing the first diagonal sum from 27 to 29 and the second diagonal from 26 to 30, my program gives a unique answer. See below
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5 4 1 8
8 9 4 5
6 9 8 9
8 3 6 8
Re:What are they teaching instead of basic algebra (Score:5, Informative)
I wrote a small program to find all solutions. If I did not make any mistake in my program the problem in the newspaper one has exactly 46 solutions
I used MiniZinc [minizinc.org] to model the problem and can confirm that there are 46 solutions. If you remove the 1-9 digit value constraint, there are 369 solutions.
Re: (Score:2)
Re: What are they teaching instead of basic algebr (Score:2)
Certainly! It's also worth checking out Hakan Kjellerstrand's MiniZinc page. It has lots of example models and puzzles:
http://www.hakank.org/minizinc... [hakank.org]
"10 Minutes 12 Seconds"... (Score:1)
... is probably a hint on the fact that there are 10 equations and 12 variables :-)
The warning (Score:2)
"when the puzzle is syndicated newspapers are supposed to warn readers that there's multiple solutions"
Really? Is that some sort of a known convention? And what does syndication have to do with it?
And hos is this unusual? (Score:2)
Mistakes are made all the time - you might not believe it, but newspapers rarely publish puzzles, even syndicated ones, without some editing beforehand. Often puzzles like Sudokus, crosswords, and such have to be re-drawn because they're not in a format the paper needs - often signified by textual elements being razor sharp while graphical elements are blurry or pixellated because the format wasn't camera ready, or the printing plate machine can't handle it or it needs reformatting, etc.
And when that happen
Not impossible (Score:2)
Possible is in Impossible