neighbour of my current position of "character or number"

example number 2 neighbour number = 1,3,5,6,7

number 7 neighbour number = 2,3,4,6,8,10,11,12

number 12 neighbour number = 7,8,11,3,16

and 16 inside the 12 neighbour's numbers so "2,7,12,16" consider related each others so should return "true".

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.

Hi; Je suis Charlie , Thanks for describe more detail on my question. But 2,4,7,12 are the chain/linkages with each other so should return true. 2 link with 7 and 7 link with 4 . something like A-star pathFinder.