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)