LeetCode 147. 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 head;
        ListNode* term = head->next;
        ListNode* term2 = head;
        
        ListNode* pre = head;
        ListNode* pre2 ;
        int tag;
        while(term!=NULL)
        {
            tag=0;
            while(term2!=term)
            {
               if( term->val < term2->val)
               {
                   pre->next = term->next;
                   
                   term->next = term2;
                   if(pre2!=NULL)
                       pre2->next = term;
                   else
                       head = term;
                   
                  
                   term = pre->next;
                   tag=1;
                   break;
               }
               pre2 = term2;
               term2 = term2->next;
            }
            pre2 = NULL;
            term2 = head;
            if(tag==1)
                continue;
            pre = term;
            term = term->next;
        }
        
        return head;
        
    }
};