Insertion Sort List

public class Solution {
public ListNode insertionSortList(ListNode head) {
// 想清楚怎么插入就很简单啦
if(head==null|| head.next ==null) return head;
ListNode h =  new ListNode(-1);
//  h.next = head; // 不是原位排序
ListNode  cur = head;
while(cur!=null){
// 要重新定义pre的指向！！！
ListNode pre = h;
ListNode t = cur.next;
while(pre.next!=null && pre.next.val<=cur.val){
pre = pre.next;
}
cur.next = pre.next;
pre.next = cur;
cur = t;
}
return h.next;
}
}