linkedlist: add at index done

Author: Ram swaroop

src/me/ramswaroop/Main.java

@@ -98,22 +98,32 @@ public static void main(String[] args) {
                         out.println("Select operation:");
                         out.println("=================");
                         out.println("1. Add");
-                        out.println("2. Remove");
-                        out.println("3. Print");
-                        out.println("4. Exit module");
+                        out.println("2. Add at index");
+                        out.println("3. Remove");
+                        out.println("4. Print");
+                        out.println("5. Exit module");
                         k2 = Integer.parseInt(in.nextLine());
+                        int input, index;
                         switch (k2) {
                             case 1:
                                 out.println("Enter value:");
-                                int input = Integer.parseInt(in.nextLine());
+                                input = Integer.parseInt(in.nextLine());
                                 singleLinkedList.add(input);
                                 singleLinkedList.printList();
                                 break;
                             case 2:
-                                out.println("Removed element: " + singleLinkedList.remove());
+                                out.println("Enter value:");
+                                input = Integer.parseInt(in.nextLine());
+                                out.println("Enter index:");
+                                index = Integer.parseInt(in.nextLine());
+                                singleLinkedList.add(index, input);
                                 singleLinkedList.printList();
                                 break;
                             case 3:
+                                out.println("Removed element: " + singleLinkedList.remove());
+                                singleLinkedList.printList();
+                                break;
+                            case 4:
                                 singleLinkedList.printList();
                                 break;
                             case 5:

src/me/ramswaroop/linkedlists/SingleLinkedList.java

@@ -34,7 +34,28 @@ public boolean add(E item) {
 
     @Override
     public boolean add(int index, E item) {
-        return false;
+        // base case
+        if (index > size) {
+            throw new IndexOutOfBoundsException("LinkedList isn't long enough.");
+        }
+        // linkedlist is empty
+        if (head == null) {
+            head = new Node<>(item, null);
+        } else if (index == 0) { // add at first
+            Node<E> newNode = new Node<>(item, head);
+            head = newNode;
+        } else { // add at any other location
+            Node<E> curr = head;
+            int i = 0;
+            while (i < index - 1) {
+                curr = curr.next;
+                i++;
+            }
+            Node<E> newNode = new Node<>(item, curr.next);
+            curr.next = newNode;
+        }
+        size++;
+        return true;
     }
 
     @Override
@@ -79,7 +100,9 @@ public E getLast() {
 
     @Override
     public E remove() {
-        return null;
+        E item = head.item;
+        head = head.next;
+        return item;
     }
 
     @Override