find permutations

permute.rb

# find arrangements of numbers from 1 to 8, so that
# if they're put into matrix like this, no consequentive numbers
# would "touch" directly or diagonally.
#    0 1
#  2 3 4 5
#    6 7

next_neighbours = [[1,2,3,4], [3,4,5], [3,6], [4,6,7], [5,6,7], [7], [7]]
result = [*1..8].permutation.filter do |row|
   next_neighbours.each_with_index.none? do |neighbours, current|
     neighbours.any? do |neighbour|
       (row[current] - row[neighbour]).abs == 1
     end
   end
end