pallindromic

# The decimal number, 585 = 10010010012 (binary), is palindromic in both bases.
# Find the sum of all numbers, less than one million, which are palindromic in base 10 and base 2.
# (Please note that the palindromic number, in either base, may not include leading 0's)

# Naive approach - TODO: needs to avoid checking both base 2 and base 10 if base 10 isn't pallindromic
def palindromic?(n, base = 10)
  numbers = n.to_s(base).split("")
  middle = numbers.length / 2.0
  first_half = numbers.slice(0, middle.ceil)
  second_half = numbers.slice(middle.floor, numbers.length)

  first_half == second_half.reverse
end

puts (1..1_000_000).select { |n|
  [10, 2].all? { |base| palindromic?(n, base) }
}.inject(&:+)