#=
Created on 28 Jul 2021

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

Solution for Problem 17 of Project Euler
https://projecteuler.net/problem=17
=#

function num2letters(num)
    nums = Dict(
        0 => "", 1 => "one", 2 => "two", 3 => "three", 4 => "four", 5 => "five",
        6 => "six", 7 => "seven", 8 => "eight", 9 => "nine", 10 => "ten",
        11 => "eleven", 12 => "twelve", 13 => "thirteen", 14 => "fourteen",
        15 => "fifteen", 16 => "sixteen", 17 => "seventeen", 18 => "eighteen",
        19 => "nineteen", 20 => "twenty", 30 => "thirty", 40 => "forty",
        50 => "fifty", 60 => "sixty", 70 => "seventy", 80 => "eighty",
        90 => "ninety", 100 => "hundred", 1000 => "thousand"
)

    if num <= 20
        return length(nums[num])
    elseif num < 100
        tens, units = divrem(num, 10)
        return length(nums[tens * 10]) + num2letters(units)
    elseif num < 1000
        hundreds, rest = divrem(num, 100)
        if rest != 0
            return num2letters(hundreds) + length(nums[100]) + length("and") + num2letters(rest)
        else
            return num2letters(hundreds) + length(nums[100])
        end
    else
        thousands, rest = divrem(num, 1000)
        return num2letters(thousands) + length(nums[1000])
    end
end

function Problem17()
    #=
    If the numbers 1 to 5 are written out in words: one, two, three, four,
    five, then there are 3 + 3 + 5 + 4 + 4 = 19 letters used in total.

    If all the numbers from 1 to 1000 (one thousand) inclusive were written
    out in words, how many letters would be used?

    NOTE: Do not count spaces or hyphens. For example, 342 (three hundred and
    forty-two) contains 23 letters and 115 (one hundred and fifteen) contains
    20 letters. The use of "and" when writing out numbers is in compliance
    with British usage.
    =#
    n = 1000
    letters = 0
    for num in 1:n
        letters += num2letters(num)
    end
    return letters
end


println("Time to evaluate Problem 17:")
@time Problem17()
println("")
println("Result for Problem 17: ", Problem17())