solution.rb

def except(input)
  input.map.with_index.with_object([]) { |(_e, i), r| r << (r.last || 1) * (i.zero? ? 1 : input[i - 1]) }
end

def solution(input)
  except(input).zip(except(input.reverse).reverse).map { |pair| pair.inject(:*) }
end