328.奇偶链表

/*** 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 null;}ListNode evenHead = head.next;ListNode odd = head,even = evenHead; //odd始终指向奇数，even指向偶数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;}
}