September 2017 Update

Task/Average-loop-length/Kotlin/average-loop-length.kotlin

@@ -0,0 +1,38 @@
+const val NMAX  = 20
+const val TESTS = 1000000
+val rand = java.util.Random()
+
+fun avg(n: Int): Double {
+    var sum = 0
+    for (t in 0 until TESTS) {
+        val v = BooleanArray(NMAX)
+        var x = 0
+        while (!v[x]) {
+            v[x] = true
+            sum++
+            x = rand.nextInt(n)
+        }
+    }
+    return sum.toDouble() / TESTS
+}
+
+fun ana(n: Int): Double {
+    val nn = n.toDouble()
+    var term = 1.0
+    var sum = 1.0
+    for (i in n - 1 downTo 1) {
+        term *= i / nn
+        sum += term
+    }
+    return sum
+}
+
+fun main(args: Array<String>) {
+    println(" N    average    analytical    (error)")
+    println("===  =========  ============  =========")
+    for (n in 1..NMAX) {
+        val a = avg(n)
+        val b = ana(n)
+        println(String.format("%3d   %6.4f   %10.4f      (%4.2f%%)", n, a, b, Math.abs(a - b) / b * 100.0))
+    }
+}