Insertion Sort List

Sort a linked list using insertion sort.
 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     {
13         
14         if(head == NULL || head->next == NULL)
15             return head;
16         
17         vector<int> vec;
18         ListNode *p = head;
19         while(p != NULL)
20         {
21             vec.push_back(p->val);
22             p = p->next;
23         }
24         
25         for(int i = 1; i < vec.size(); i++)
26         {
27             int tmp = vec[i];
28             int j;
29             for(j = i; j > 0 && tmp < vec[j-1]; j--)
30                 vec[j] = vec[j-1];
31                 
32             vec[j] = tmp;
33         }
34         
35         p = head;
36         for(vector<int>::iterator it = vec.begin(); it != vec.end(); it++, p = p->next)
37             p->val = *it;
38             
39         return head;
40     }
41 };