rodrigovidal

let sumAllMultiplesOf3Or5 list = 
    let mutable total = 0
    for i in list do
        if i % 3 = 0 || i % 5 = 0 then
            total <- total + i
    total
         

rodrigovidal

let isMultipleOf3Or5 x = x % 3 = 0 || x % 5 = 0

let sumAllMultiplesOf3Or5 list = List.sum (List.filter isMultipleOf3Or5 list)

rodrigovidal

let isMultipleOf3Or5 x = x % 3 = 0 || x % 5 = 0

let sumAllMultiplesOf3Or5Ref list = 
    list |> List.filter isMultipleOf3Or5 
         |> List.sum

rodrigovidal

let factorize n =
    let rec find i =
        if i >= n then None
        elif (n % i = 0) then Some(i, n/i)
        else find(i+1)
    find 2

rodrigovidal

open System
open System.Collections.Generic

let sieve n = 
    seq {
        let hash = new HashSet<int64>()
        yield 2L
        for k in 3L..2L..System.Int64.MaxValue do
            if not (hash.Contains k) then
                yield k

rodrigovidal

let sieveOfEratosthenes n = 
    let arr = [| for i in 0..n -> 1 |]
    let sqrt = sqrt(float n) |> int
    for k = 2 to sqrt + 1 do
        if arr.[k] = 1 then
            for j in 2*k..k..n-1 do
                arr.[j] <- 0
    seq { for i in 2..n-1 do if arr.[i] = 1 then yield i }

rodrigovidal

let fibonacci =
    (0, 1) 
    |> Seq.unfold(fun (current, next) -> Some(current, (next, current + next)))
    |> Seq.takeWhile(fun x -> x <= 4000000)
    |> Seq.filter(fun x -> x % 2 = 0)
    |> Seq.sum

rodrigovidal

private int SumNumbers(int from, int to)
{
    int res = 0;
    for (int i = from; i <= to; i++)
        res = res + 1;
    return res;
}

rodrigovidal

private int SumNumbers(int from, int to)
{
    if (from > to) return 0;
    int sumRest = SumNumbers(from + 1, to);
    return from + sumRest;
}

rodrigovidal

public int SumNumbers(int from, int to)
{
    return from > to ? 0 : (SumNumbers(from + 1, to) + from) ;
}