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

Armstrong Numbers

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.

Permalink: http://problemotd.com/problem/armstrong-numbers/

Comments:

  • Jason Brady - 11 years 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 - 11 years ago

    Nicely done

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  • PyBanana - 11 years 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 - 11 years ago

    I love these python one liners. Good stuff

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  • asheehan - 11 years 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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