LeetCode-328.Odd Even Linked List

https://leetcode.com/problems/odd-even-linked-list/

Given a singly linked list, group all odd nodes together followed by the even nodes. 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(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 was in the input. 

The first node is considered odd, the second node even and so on ...

这道题并不难，分别把奇偶节点单独取出来就好

/**
* Definition for singly-linked list.
* public class ListNode {
* public int val;
* public ListNode next;
* public 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=head.next;
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;
}
}