"Linked list" Odd even Linked List

Topic:

Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we is 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 (1) Space complexity and O (nodes) time complexity.

Example:
Given 1->2->3->4->5->NULL ,
Return 1->3->5->2->4->NULL .

Note:
The relative order inside both the even and odd groups should remain as it is in the input.
The first node is considered odd, the second node even ...

Ideas:

This problem only takes the odd and even nodes out to form two linked lists, and then merges them.

/** Definition for singly-linked list. * Function ListNode (val) {* This.val = val; * This.next = null; *} 
    *//** * @param {listnode} head * @return {ListNode}*/varOddevenlist =function(head) {if(head==NULL|| head.next==NULL){        returnHead; }        varp=head.next.next,ohead=head,ehead=head.next,i=3,op=ohead,ep=Ehead;  while(p!=NULL){        if(i%2!=0) {Op.next=p; Op=Op.next; }Else{Ep.next=p; EP=Ep.next; } P=P.next; I++; } Ep.next=NULL; Op.next=Ehead; returnOhead;};

"Linked list" Odd even Linked List