New Puzzle Challenges Math Skills | Hacker News Reader

New Puzzle Challenges Math Skills

nytimes.com

16 pointsjaydub8 comments

I got really addicted to KenKen, but I couldn't find a good source of unlimited puzzles, so I made my own puzzle generator

http://mattdonahoe.com/numnum/print

It was a quick thing I did one night. No error/win checking and only supports multiplication.

Later I found http://www.webkendoku.com/ but I still use my iphone version http://mattdonahoe.com/numnum/iphone

From the article: "¶Look for cages whose target numbers are unusually high or low for their number of squares. Often these have unique answers. For example, in a six-by-six puzzle, two squares with a sum of 11 must be filled with 5 and 6, in some order. Three squares with a product of 10 must be 1, 2 and 5."

Why must two squares with a sum of 11 be filled with 5 and 6?

A 6x6 puzzle runs from 1-6.

The real test is coding the solver, or, for the theorists, proving the lower bounds runtime for such a solver.

Sorry, but I'm not getting it. If there are two boxes together with the label "6x", does that mean that six times the first square should equal the second square? If so, how are we to interpret the 120x? If not, what's the meaning?

From what I understand you're supposed to get the result (in your example 6) by combining the cells in that box with the given operator (in this case times).

So a "6x" box with two cells results in (1 and 6) or (2 and 3), since those are the only products that result in 6. Likewise, "7+" with three squares can only be (1, 2 and 4).

7+ could also be 1,3,3 or 3,2,2 if the box is L-shaped so that the equal numbers don't go in the same row or column.

It is also important to note as it states in the article that order does not matter in these operations. Clearly it does not matter in addition or multiplication but say two boxes are outlined with "3-" the contents of the two boxes could be 4,1 or 1,4 in either order.

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