leetcode. Insertion Sort List

 1 ListNode *insertionSortList(ListNode *head) 
 2     {
 3         ListNode *dummy = new ListNode(INT_MIN), *p, *q, *r;
 4         ListNode *new_head;
 5         dummy->next = head;
 6         
 7         p = dummy->next;
 8         while (p != NULL)
 9         {
10             q = p->next;
11             if (q == NULL)
12                 break;
13             for (r = dummy; r->next != q; r = r->next)
14             {
15                 if (q->val <= r->next->val)
16                     break;
17             }
18             if (r->next == q)
19             {
20                 p = p->next;
21                 continue;
22             }
23             p->next = q->next;
24             q->next = r->next;
25             r->next = q;
26         }
27         
28         new_head = dummy->next;
29         delete dummy;
30         return new_head;
31     }