Problem of the Day
A new programming or logic puzzle every Mon-Fri

Today's objective is to create a program that finds all the Armstrong Numbers from 10 to 10000 inclusive. An Armstrong Number is a number that is the sum of its own digits each raised to the power of the number of digits. For example, 153 is considered an Armstrong Number 1^3 + 5^3 +3^3 = 153.

Comments:

• Jason Brady - 10 years, 3 months ago

  In Haskell

  main :: IO ()
  main = print $ filter isArmstrong [10..10000]
  
  isArmstrong :: Int -> Bool
  isArmstrong n = armstrong n == n
    where 
      armstrong 0 = 0
      armstrong x = d^p + armstrong r
        where (r, d) = x `divMod` 10
      p = length $ digits n
      digits 0 = []
      digits x = d : digits r
        where (r, d) = x `divMod` 10
  

  Output is

  [153,370,371,407,1634,8208,9474]

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• Max Burstein - 10 years, 3 months ago

  Nicely done

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• PyBanana - 10 years, 3 months ago

  Python 2.7 one liner!

  print [i for i in range(10,10000) if sum(int(j) ** len(str(i)) for j in str(i)) == i]
  

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• Max Burstein - 10 years, 3 months ago

  I love these python one liners. Good stuff

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• asheehan - 10 years, 3 months ago

  With Ruby

  def isArmstrongNumber(input)
      length = input.to_s.size
      digits = input.to_s.chars.map(&:to_i)
      sum = 0
      digits.each do |digit|
          sum = sum + digit ** length
      end
  
      return sum == input
  end
  
  armstrongNumbers = Array.new
  for i in 10..10000
      if isArmstrongNumber(i)
          armstrongNumbers.push i
      end
  end
  
  puts armstrongNumbers
  

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