So, it seems to be a graphical neighborhood, if I understand correctly. For example, in this matrix: 
( [ x, x, x, x, x],
  [ x, y, y, y, x],
  [ x, y, z, y, x],
  [ x, y, y, y, x],
  [ x, x, x, x, x],
)

[download]
the "y" elements are all neighbors of "z", but the "x" elements are not. Is my understanding correct?

But I still don't see why [2, 4, 7, 12] should pass successfully your test in your original data set: 

( [ 1,  2,  3,  4,],
  [ 5,  6,  7,  8,],
  [ 9, 10, 11, 12,],
  [13, 14,  3, 16,],
  [ 2, 18, 19, 20,] )

[download]
2 and 4 are not neighbors.

Or did I miss something?

Je suis Charlie.

In reply to Re^7: perl array matrix by Laurent_R
in thread perl array matrix by perlhelp

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