Added obligatory assignments

src/assignment/week5/games/game2048/Game2048Helper.kt

@@ -0,0 +1,41 @@
+package games.game2048
+
+/*
+ * This function moves all the non-null elements to the beginning of the list
+ * (by removing nulls) and merges equal elements.
+ * The parameter 'merge' specifies the way how to merge equal elements:
+ * it returns a new element that should be present in the resulting list
+ * instead of two merged elements.
+ *
+ * If the function 'merge("a")' returns "aa",
+ * then the function 'moveAndMergeEqual' transforms the input in the following way:
+ *   a, a, b -> aa, b
+ *   a, null -> a
+ *   b, null, a, a -> b, aa
+ *   a, a, null, a -> aa, a
+ *   a, null, a, a -> aa, a
+ *
+ * You can find more examples in 'TestGame2048Helper'.
+*/
+fun <T : Any> List<T?>.moveAndMergeEqual(merge: (T) -> T): List<T> {
+    val mutableList = mutableListOf<T>()
+    val oldList = filterNotNull()
+
+    var index = 0
+    while (true) {
+        if (index >= oldList.size) break
+
+        val first = oldList[index]
+        val second = oldList.getOrNull(index + 1)
+
+        if (first == second) {
+            index += 2
+            mutableList.add(merge(first))
+        } else {
+            index += 1
+            mutableList.add(first)
+        }
+    }
+    return mutableList
+}
+