Initial data commit

Task/Singly-linked-list-Element-insertion/Groovy/singly-linked-list-element-insertion-1.groovy

@@ -0,0 +1,20 @@
+class NodeList {
+    private enum Flag { FRONT }
+    private ListNode head
+    void insert(value, insertionPoint=Flag.FRONT) {
+        if (insertionPoint == Flag.FRONT) {
+            head = new ListNode(payload: value, next: head)
+        } else {
+            def node = head
+            while (node.payload != insertionPoint) {
+                node = node.next
+                if (node == null) {
+                    throw new IllegalArgumentException(
+                        "Insertion point ${afterValue} not already contained in list")
+                }
+            }
+            node.next = new ListNode(payload:value, next:node.next)
+        }
+    }
+    String toString() { "${head}" }
+}

Task/Singly-linked-list-Element-insertion/Groovy/singly-linked-list-element-insertion-2.groovy

@@ -0,0 +1,7 @@
+def list = new NodeList()
+list.insert('B')
+list.insert('A')
+println list
+
+list.insert('C', 'A')
+println list