[LeetCode] 328. Odd Even Linked List

奇偶链表。题意是给一个链表，请按照node的奇偶性重新排列，奇数在前，偶数在后。注意不是按照node.val而是按照node number。例子，

没什么好解释的，看懂代码，思路也就看懂了。

时间O(n)

空间O(1)

 1 /**
 2  * Definition for singly-linked list.
 3  * function ListNode(val) {
 4  *     this.val = val;
 5  *     this.next = null;
 6  * }
 7  */
 8 /**
 9  * @param {ListNode} head
10  * @return {ListNode}
11  */
12 var oddEvenList = function(head) {
13     // corner case
14     if (head === null || head.next === null) {
15         return head;
16     }
17
18     // normal case
19     let first = head;
20     let second = head.next;
21     let secondHead = second;
22     while (second !== null && second.next !== null) {
23         first.next = first.next.next;
24         second.next = second.next.next;
25         first = first.next;
26         second = second.next;
27     }
28     first.next = secondHead;
29     return head;
30 };