leetcode-Insertion Sort List

class Solution {
public:
ListNode* insertionSortList(ListNode* head) {
if(head == NULL || head->next == NULL)
{
return head;
}
ListNode dummy(-1);
dummy.next = head;

ListNode *pre = head;
ListNode *cur = head->next;
while(cur != NULL)
{
if(cur->val >= pre->val)
{
pre = cur;
cur = cur->next;
}
else
{
ListNode *insertPre = &dummy;
ListNode *insertCur = dummy.next;
while(insertCur->val < cur->val)
{
insertPre = insertCur;
insertCur = insertCur->next;
}
pre->next = cur->next;
cur->next = insertCur;
insertPre->next = cur;
cur = pre->next;
}
}
return dummy.next;
}
};