Insertion Sort List

Sort a linked list using insertion sort.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *insertionSortList(ListNode *head) 
    {
        
        if(head == NULL || head->next == NULL)
            return head;
        
        vector<int> vec;
        ListNode *p = head;
        while(p != NULL)
        {
            vec.push_back(p->val);
            p = p->next;
        }
        
        for(int i = 1; i < vec.size(); i++)
        {
            int tmp = vec[i];
            int j;
            for(j = i; j > 0 && tmp < vec[j-1]; j--)
                vec[j] = vec[j-1];
                
            vec[j] = tmp;
        }
        
        p = head;
        for(vector<int>::iterator it = vec.begin(); it != vec.end(); it++, p = p->next)
            p->val = *it;
            
        return head;
    }
};