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||head->next==NULL)
            return head;
        ListNode*fixflag=new ListNode(0);
        ListNode* start,*end,*pre,*flag;
        start=head;
        end=start->next;
        pre=start;
        fixflag->next=start;
        flag=fixflag;
        while(end!=NULL)
        {
        while(flag->next!=end)
        {
            if(end->val<=flag->next->val)
            {
                pre->next=end->next;
                end->next=flag->next;
                flag->next=end;
                end=pre->next;
                flag=fixflag;
                break;
            }
            flag=flag->next;
        }
        if(flag->next==end)
        {
            flag=fixflag;
            end=end->next;
            pre=pre->next;
            
        }
        
        }
        return fixflag->next;
        
    }
};