Odd Even Linked List

Leetcode 328.

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode oddEvenList(ListNode head) {
       if(head == null)
         return head; 
       ListNode odd = head, even = head.next, evenHead = even;
       while(even != null && even.next != null){
           //process the odd 
           odd.next = odd.next.next; 
           odd = odd.next; 
           //process the even
           even.next = even.next.next;
           even = even.next; 
       }
       odd.next = evenHead;
    return head;
    }
}