1 /**
2 * Definition for singly-linked list.
3 * public class ListNode {
4 * int val;
5 * ListNode next;
6 * ListNode(int x) { val = x; }
7 * }
8 */
9 public class Solution {
10 public ListNode insertionSortList(ListNode head) {
11 if(head==null) return head;//corner case:if the List is null;
12 ListNode helper = new ListNode(0);
13 ListNode pre = helper,//insert between pre and pre.next
14 cur = head,//the node will be inserted
15 next = null;//the next node will be valued by cur
16 while(cur!=null){
17 next = cur.next;
18 // find the right place to insert
19 while(pre.next!=null&&pre.next.val<cur.val){
20 pre= pre.next;
21 }
22 // insert between pre and pre.next
23 cur.next = pre.next;
24 pre.next = cur;
25 pre = helper;
26 cur = next;
27 }
28 return helper.next;
29 }
30 }
31 // as for the run time complexity,for the worst case, it will cost O(n^2) time. As for the space complexity,it will take O(n)
