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Problem 780. Give a matrix that matches itself when rotated

Created by Ned Gulley

Given n and s, return a n-by-n matrix a of integers such that

 sum(sum(a == rot90(a))) 

is equal to exactly s. The integers should be chosen from the set 1 to n.

So for instance, if n is 2, and s is 2, you could return

 a = [ 1 1 
       2 2 ] 

since rot90(a) matches a in exactly one place.

For any n and s, a is of course not unique. I'm only checking to make sure the conditions are true.

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16 correct solutions 10 incorrect solutions
Last solution submitted on Feb 13, 2014

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