June 2018 Update

Task/Pick-random-element/Kotlin/pick-random-element.kotlin

@@ -1,13 +1,30 @@
-// version 1.0.6
+// version 1.2.10
+
+import java.util.Random
+
+/**
+ * Extension function on any list that will return a random element from index 0
+ * to the last index
+ */
+fun <E> List<E>.getRandomElement() = this[Random().nextInt(this.size)]
+
+/**
+ * Extension function on any list that will return a list of unique random picks
+ * from the list. If the specified number of elements you want is larger than the
+ * number of elements in the list it returns null
+ */
+fun <E> List<E>.getRandomElements(numberOfElements: Int): List<E>? {
+    if (numberOfElements > this.size) {
+        return null
+    }
+    return this.shuffled().take(numberOfElements)
+}
 
 fun main(args: Array<String>) {
     val list = listOf(1, 16, 3, 7, 17, 24, 34, 23, 11, 2)
-    println("The list consists of the following numbers:")
-    println(list)
-    val chosen = mutableSetOf<Int>()
-    println("\nFive elements chosen at random without duplication are:")
-    while (chosen.size < 5) {
-        val r = list[(Math.random() * list.size).toInt()]
-        if (chosen.add(r)) println(r)
-    }
+    println("The list consists of the following numbers:\n${list}")
+
+    // notice we can call our extension functions as if they were regular member functions of List
+    println("\nA randomly selected element from the list is ${list.getRandomElement()}")
+    println("\nA random sequence of 5 elements from the list is ${list.getRandomElements(5)}")
 }