leetcode---Insertion Sort List

/**
* 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)
return NULL;

ListNode *start = new ListNode(0);
ListNode *cur = head;

while(cur)
{
ListNode *pre = start;
while(pre->next && cur->val > pre->next->val)
{
pre = pre->next;
}
ListNode *next = cur->next;
cur->next = pre->next;
pre->next = cur;
cur = next;
}
return start->next;
}
};