Pi approximate calculation by Monte Carlo method. Inspired by https://www.weheartswift.com/random-pi/.

pi_monte_carlo.swift

func piCalc(_ totalPoints: Int) -> Double {
    var nPointsInside = 0
    for _ in 1...totalPoints {
        let (x, y) = (drand48() * 2 - 1, drand48() * 2 - 1)
        if x * x + y * y <= 1 {
            nPointsInside += 1
        }
    }
    return 4.0 * Double(nPointsInside) / Double(totalPoints)
}