Cacher is the code snippet organizer for pro developers

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

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