Given a singly linked list, write a program to group all odd nodes together followed by the even nodes.

Problem Note

  • Please note here we are talking about the node number and not the value in the nodes.
  • You should try to do it in place.
  • The program should run in O(n) time complexity.
  • The relative order inside both the even and odd groups should remain as it was in the input.
  • The first node is considered odd, the second node even, and so on.

Example 1 

Input: 1->2->3->4->5->NULL
Output: 1->3->5->2->4->NULL
Explanation: The first group is of elements at odd position (1,3,5) in the linked list and then the ones at the even position(2,4)

Example 2 

Input: 2->1->3->5->6->4->7->NULL
Output: 2->3->6->7->1->5->4->NULL
Explanation: The first group is of elements at odd position (2,3,6,7) in the linked list and then the ones at the even position(1,5,4)