added initial Kotlin puzzlers

Author: Iurii-Dziuban

src/test/kotlin/org/kotlin/examples/PuzzlesTest.kt

@@ -0,0 +1,98 @@
+package org.kotlin.examples
+
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+/**
+ * To look at
+ * https://github.com/angryziber/kotlin-puzzlers
+ */
+class PuzzlesTest {
+
+    enum class E { e }
+
+    @Test
+    fun exhaustiveEnum() {
+        val en = E.e
+        val a = when (E.e) {
+            en -> "1" // will be known at the runtime so else/other branches should be covered
+            PuzzlesTest.E.e -> "2"
+        }
+        assertEquals("1", a)
+    }
+
+    //ClosedRange.contains() converts parameter into Int before checking
+    @Test
+    fun inclusiveRange() {
+        val i = 10.5
+        var res = ""
+        when (i) {
+            in 1..10 -> res = "in"
+            !in 1..10 -> res = "!in"
+            else -> res = "else"
+        }
+        assertEquals("in", res)
+    }
+
+    @Test
+    fun eagerOrLazy() {
+        //eager
+        val x = listOf(1, 2, 3).filter { print("$it "); it >= 2 }
+        println()
+        assertEquals(5, x.sum())
+        // lazy
+        val y = sequenceOf(1, 2, 3).filter { print("$it "); it >= 2 }
+        println()
+        assertEquals(5, y.sum())
+        // or
+        val z = listOf(1, 2, 3).asSequence().filter { print("$it "); it >= 2 }
+        println()
+        assertEquals(5, z.sum())
+    }
+
+    @Test(expected = UnsupportedOperationException::class)
+    fun isMutable() {
+        val readonly = listOf(1, 2, 3)
+
+        if (readonly is MutableList) {
+            readonly.add(4)
+        }
+
+        assertEquals(readonly, listOf(1,2,3))
+    }
+
+    @Test
+    fun inclusiveRanges() {
+        val range = 0..9 step 3
+
+        assertEquals("0, 3, 6, 9", range.joinToString())
+    }
+
+    @Test
+    fun mapWithDefault() {
+        val map = mapOf<Any, Any>().withDefault{ "default" }
+        assertNull(map["1"])
+    }
+
+    @Test
+    fun reversedRanges() {
+        val range = 0..10
+
+        val reverseThenStep = range.reversed().step(3).toList()
+        val stepThenReverse = range.step(3).reversed().toList()
+
+        assertEquals(listOf(10, 7, 4, 1), reverseThenStep)
+        assertEquals(listOf(9, 6, 3, 0), stepThenReverse)
+    }
+
+    @Test
+    fun sorted() {
+        val list = arrayListOf(1, 5, 3, 2, 4)
+
+        val sortedList = list.sort()
+
+        assertTrue(sortedList is kotlin.Unit)
+    }
+}