leetcode-328. Odd Even Linked List

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

Credits:
Special thanks to @DjangoUnchained for adding this problem and creating all test cases.

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思路:题目意思是找奇偶链表，奇数点放前面，偶数点放后面，这里是指节点不是值。
代码如下:

/** * 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 head;        ListNode even=head.next;        ListNode odd=head;        ListNode temp=even;        while(even!=null&&even.next!=null){            odd.next=even.next;            odd=odd.next;            even.next=odd.next;            even=even.next;        }        odd.next=temp;        return head;    }}