This post has two puzzles!

**Latin Square** Put an integer between 1 and the length of the grid (5) inclusive such that each row/column has each number exactly once.

**Expected difficulty** Easy • Answer • Comment/E-mail if you want a solution to be published

Puzzle 75: TomTom is NP-complete

Latin Square

**TomTom** Put an integer between 1 and the length of the grid (10) inclusive such that each row/column has each number exactly once. The number at the top-left of each region indicates the value of a mathematical operation (addition, subtraction, multiplication, division) applied successively to all digits in the cage, starting with the largest digit for subtraction and division (e.g. 1,2,4 with subtraction is a 1- clue as 4-2-1 = 1). (Description from Grandmaster Puzzles)

**Expected difficulty** Easy • Answer • Comment/E-mail if you want a solution to be published

Puzzle 75: TomTom is NP-complete

TomTom

I guess the two puzzles above prove that TomTom is NP-complete. We can see a trivial polynomial transformation from a Latin Square to a TomTom, and Latin Square is NP-complete.

So, sorry for Jacob Lance.

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Sigh… -_-

Well, it will still look like a good project, my science teacher doesn’t have to know about this…

I was planning on posting my NP-complete TomTom on Friday, and I guess I still will, its just very anti-climactic now

Heh, you can argue that proving Latin Square is NP-complete is by itself hard, while 3-SAT is very well-known. 😛

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