#=
Created on 08 Sep 2021

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

Solution for Problem 38 of Project Euler
https://projecteuler.net/problem=38 =#

using BenchmarkTools

function Problem38()
    #=
    Take the number 192 and multiply it by each of 1, 2, and 3:

      192 × 1 = 192
      192 × 2 = 384
      192 × 3 = 576

    By concatenating each product we get the 1 to 9 pandigital,
    192384576. We will call 192384576 the concatenated product of
    192 and (1,2,3)

    The same can be achieved by starting with 9 and multiplying by
    1, 2, 3, 4, and 5, giving the pandigital, 918273645, which is
    the concatenated product of 9 and (1,2,3,4,5).

    What is the largest 1 to 9 pandigital 9-digit number that can
    be formed as the concatenated product of an integer with
    (1,2, ... , n) where n > 1? =#

    results = []
    pandigital = join(['1', '2', '3', '4', '5', '6', '7', '8', '9'])
    # Number must 4 digits (exactly) to be pandigital
    # if n > 1
    for i in 1:10_000
        integer = 1
        number = ""
        while length(number) < 9
            number *= string(integer * i)
            if join(sort(collect(number))) == pandigital
                push!(results, number)
            end
            integer += 1
        end
    end
    return maximum(results)
end


println("Time to evaluate Problem $(lpad(38, 3, "0")):")
@btime Problem38()
println("")
println("Result for Problem $(lpad(38, 3, "0")): ", Problem38())