gistfile1.txt

def gen_index(num_ele)
  arr = []
  num_ele.times do |index|
    arr = add_index(arr, index)
  end
  arr
end

def add_index(arr, index)
  arr + arr.reverse.map { |ele| ele.dup << index } << [index]
end

puts "gen 1"
gen_index(1).each {|e| p e}
puts "gen 2"
gen_index(2).each {|e| p e}
puts "gen 3"
gen_index(3).each {|e| p e}
puts "gen 4"
gen_index(4).each {|e| p e}