Added Monte Carlo in Swift 4.1

chapters/monte_carlo/code/swift/monte_carlo.swift

@@ -0,0 +1,57 @@
+//Double Extension from YannickSteph on StackOverflow: https://stackoverflow.com/questions/25050309/swift-random-float-between-0-and-1
+
+import Foundation
+
+
+
+public extension Double {
+
+    public static var random: Double {
+
+        return Double(arc4random()) / 0xFFFFFFFF // Returns a random double between 0.0 and 1.0, inclusive.
+    }
+
+    public static func random(min: Double, max: Double) -> Double {
+
+        return Double.random * (max - min) + min
+    }
+}
+
+
+func isInCircle(x: Double, y: Double, radius: Double) -> Bool {
+
+    return (x*x) + (y*y) < radius*radius
+}
+
+
+func monteCarlo(n: Int) -> Double {
+
+    let radius: Double = 1
+    var piCount = 0
+    var randX: Double
+    var randY: Double
+
+    for _ in 0...n {
+        randX = Double.random(min: 0, max: radius)
+        randY = Double.random(min: 0, max: radius)
+
+        if(isInCircle(x: randX, y: randY, radius: radius)) {
+            piCount += 1
+        }
+    }
+
+    let piEstimate = Double(4 * piCount)/(Double(n))
+
+    return piEstimate
+}
+
+
+func main() {
+    let piEstimate = monteCarlo(n: 10000)
+    print("Pi estimate is: ", piEstimate)
+    print("Percent error is: \(100*(Double.pi - piEstimate)/Double.pi)%")
+}
+
+
+main()
+

chapters/monte_carlo/monte_carlo.md

@@ -55,6 +55,8 @@ each point is tested to see whether it's in the circle or not:
 [import:12-14, lang:"golang"](code/go/monteCarlo.go)
 {% sample lang="java" %}
 [import:11-13, lang:"java"](code/java/MonteCarlo.java)
+{% sample lang="swift" %}
+[import:21-25, lang:"swift"](code/swift/monte_carlo.swift)
 {% endmethod %}
 
 If it's in the circle, we increase an internal count by one, and in the end,
@@ -113,6 +115,9 @@ Feel free to submit your version via pull request, and thanks for reading!
 {% sample lang="java" %}
 ### Java
 [import, lang:"java"](code/java/MonteCarlo.java)
+{% sample lang="swift" %}
+### Swift
+[import, lang:"swift"](code/java/monte_carlo.swift)
 {% endmethod %}