alphametic.rb

Result = Struct.new(:charactor, :expression, :answer)

def to_int(map, str)
  str.split(//).reduce(0) {|acc, c| acc * 10 + map[c]}
end

def alphametic(expression)
  # count uniq charactors
  charactors = Array.new(expression).join.split(//).uniq
  length = charactors.length

  ret = []

  # p = gperm((0..9).to_a, length)
  # for ary in p
  (0..9).to_a.permutation(length) do |ary|
    hash = Hash.new()
    for i in 0..(length-1)
      hash[charactors[i]] = ary[i]
    end

    # Most significant digit is non-zero
    nonZero = expression.all?{|exp| hash[exp[0]] != 0}
    if nonZero
      tmp  = expression.reduce([]) {|acc, i| acc.push to_int(hash, i)}
      ans  = tmp.pop
      calc = tmp.reduce(0) {|acc, i| acc + i}

      if (calc == ans)
        ret.push(Result.new(hash), tmp, ans)
      end
    end
  end
  ret
end

puts alphametic(["SEND", "MORE", "MONEY"])
#puts alphametic(["すももと", "ももとは", "ともだちだ"])
#puts alphametic(["オオ", "オオ", "カカオ", "オカカ"])
#puts alphametic(["EARTH", "AIR", "FIRE", "WATER", "NATURE"])