Odd even position data item shifting in LinkedList

Author: Antesh Sharma

src/main/java/com/antesh/dsa/linkedlist/OddEvenLinkedList.java

@@ -0,0 +1,70 @@
+package com.antesh.dsa.linkedlist;
+
+
+import java.util.List;
+
+/**
+ * Problem Reference: https://github.com/aniketskulkarni/coding-problems/blob/master/LeetCode/src/com/java7/problem/easy/linkedlist/OddEvenLinkedList.java
+ *
+ * Given the head of a singly linked list, group all the nodes with odd indices
+ * together followed by the nodes with even indices, and return the reordered
+ * list.
+ *
+ * The first node is considered odd, and the second node is even, and so on.
+ * Note that the relative order inside both the even and odd groups should
+ * remain as it was in the input.
+ * You must solve the problem in O(1) extra space complexity and O(n) time
+ * complexity.
+ *
+ * Input: head = [1,2,3,4,5]
+ * Output: [1,3,5,2,4]
+ */
+
+public class OddEvenLinkedList {
+    ListNode head;
+
+    class ListNode {
+        int data;
+        ListNode next;
+
+        public ListNode(int data) {
+            this.data = data;
+            this.next = null;
+        }
+    }
+
+    public void addAtTail(int data) {
+        if (head == null) {
+            head = new ListNode(data);
+            return;
+        }
+
+        ListNode currentNode = head;
+        while (currentNode.next != null) {
+            currentNode = currentNode.next;
+        }
+        ListNode newNode = new ListNode(data);
+        currentNode.next = newNode;
+    }
+
+    public static ListNode oddEvenLinkedList(ListNode head) {
+        if (head == null) {
+            return head;
+        }
+
+        ListNode currentNode = head;        //1 -> 2 -> 3 -> 4 -> 5
+
+        while (currentNode.next != null && currentNode.next.next != null) {
+            ListNode nextNode = currentNode.next;       // 2 -> 3
+            ListNode nextToNextNode = currentNode.next.next;    // 3 -> 4
+            currentNode.next = currentNode.next.next;   //1 -> 3 -> 4
+            //TODO:
+
+
+
+        }
+
+
+    }
+
+}