* function ListNode(x){
 *   this.val = x;
 *   this.next = null;
 * }
 */
/**
 * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
 *
 * 
 * @param head ListNode类 
 * @return ListNode类
 */
function oddEvenList( head ) {
    // write code here
    if(!head)    return head
    let cur = head,res1 = head.next,res2 = res1
    while(res2 && res2.next){
        cur.next = res2.next
        cur = cur.next
        res2.next = cur.next
        res2 = res2.next
    }
    cur.next = res1
    return head
}
module.exports = {
    oddEvenList : oddEvenList
};

alt