Odd Even Linked List

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.

Class Node:
    data (int)
    next (Node)

Input Format

First Parameter - Node head

Output Format

Return the Node.

Example 1 :

Input :
    LinkedList : 1 2 3 4
Output : 
    1 3 2 4 
Explanation : 
Odd elements are 1, 3 and even elements  are 2, 4. Hence, resultant linked list is  1 3 2 4. 

Example 2 :

Input :
    LinkedList : 1 2 3 4 5
Output : 
    1 3 5 2 4 
Explanation: 
Odd elements are 1, 3, 5 and even elements are 2, 4. Hence, resultant linked list is 1 3 5 2 4.

Constraints :

• The number of nodes in the linked list is in the range [0, 10⁴].
• -10⁶ <= Node.data <= 10⁶
• Expected Time Complexity: O(N).
• Expected Auxiliary Space: O(1).