1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode *insertionSortList(ListNode *head) {
12         ListNode dummy(INT_MIN);
13         ListNode *cur = head;
14         while (cur != nullptr) {
15             ListNode *pos = findInsertPos(&dummy, cur->val);
16             ListNode *temp = cur->next;
17             cur->next = pos->next;
18             pos->next = cur;
19             cur = temp;
20         }
21         return dummy.next;
22     }
23 private:
24     ListNode *findInsertPos(ListNode *before_head, int key) {
25         ListNode *pre = nullptr, *cur = before_head;
26         while (cur != nullptr && cur->val <= key) {
27             pre = cur;
28             cur = cur->next;
29         }
30         return pre;
31     }
32 };