#=
Created on 25 Aug 2021

@author: David Doblas Jiménez
@email: daviddoji@pm.me

Solution for Problem 30 of Project Euler
https://projecteuler.net/problem=30
=#

using BenchmarkTools

function power_digit_sum(pow, n)
    s = 0
    while n > 0
        (n, r) = divrem(n, 10)
        s += r^pow
    end
    return s
end

function Problem30()
    #=
    Surprisingly there are only three numbers that can be written as the sum
    of fourth powers of their digits:

        1634 = 1^4 + 6^4 + 3^4 + 4^4
        8208 = 8^4 + 2^4 + 0^4 + 8^4
        9474 = 9^4 + 4^4 + 7^4 + 4^4

    As 1 = 14 is not a sum it is not included.

    The sum of these numbers is 1634 + 8208 + 9474 = 19316.

    Find the sum of all the numbers that can be written as the sum of fifth
    powers of their digits.
    =#
    ans = sum(i for i in 2:1_000_000 if i == power_digit_sum(5, i))

    return ans
end


println("Time to evaluate Problem $(lpad(30, 3, "0")):")
@btime Problem30()
println("")
println("Result for Problem $(lpad(30, 3, "0")): ", Problem30())