Claudio Cherubino's blog Life of a Googler

4Feb/080

Project Euler in F# – Problem 16

This time we are gonna "cheat".

As in Problem 20 we have to sum the digits of a number, so we can just copy and paste the whole code and edit a single line to have a working solution.

The problem says:

2^15 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.

What is the sum of the digits of the number 2^1000?

The only difference between this exercise and the last one is the number to evaluate.

However, as for the factorial, F# already provides us with a native function for the powers of a numbers, so the final code will be:

#light
open Microsoft.FSharp.Math.BigInt

let rec digits n =
    match n with
    | n when n < 10I -> n
    | n ->
        let x, y = divmod n 10I
        y + digits x

let answer = digits (pow 2I 1000I)

If you compare this exercise with the last one, you can see that we actually changed one line, i.e. line 11.

Do you really want me to explain this code?

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