The fastest random number Generator

I'm intending to implement a random number generator via Swift 3. I have three different methods for generating an integer (between 0 and 50000) ten thousand times.

Do these generators use the same math principles of generating a value or not?

What generator is less CPU and RAM intensive?

method A:

var generator: Int = random() % 50000

method B:

let generator = Int(arc4random_uniform(50000))

method C:

import GameKit
let number: [Int] = [0, 1, 2... 50000]

func generator() -> Int {
    let random = GKRandomSource.sharedRandom().nextIntWithUpperBound(number.count)
    return number[random]
}