如何使用ruby生成数字组合？

def generate_combinations(digits, length)
  combinations = []
  generate_combinations_helper(digits, length, "", combinations)
  return combinations
end

def generate_combinations_helper(digits, length, current, combinations)
  if current.length == length
    combinations << current
    return
  end

  digits.each do |digit|
    new_current = current + digit.to_s
    generate_combinations_helper(digits, length, new_current, combinations)
  end
end

digits = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
length = 3
combinations = generate_combinations(digits, length)

puts combinations