Data commit

Task/Middle-three-digits/Kotlin/middle-three-digits.kotlin

@@ -0,0 +1,16 @@
+fun middleThree(x: Int): Int? {
+    val s = Math.abs(x).toString()
+    return when {
+        s.length < 3 -> null // throw Exception("too short!")
+        s.length % 2 == 0 -> null // throw Exception("even number of digits")
+        else -> ((s.length / 2) - 1).let { s.substring(it, it + 3) }.toInt()
+    }
+}
+
+fun main(args: Array<String>) {
+    println(middleThree(12345)) // 234
+    println(middleThree(1234)) // null
+    println(middleThree(1234567)) // 345
+    println(middleThree(123))// 123
+    println(middleThree(123555)) //null
+}