思路理清楚就好。

ListNode *partition(ListNode *head, int x) {        // Note: The Solution object is instantiated only once and is reused by each test case.        if(head==NULL)            return NULL;        ListNode* smallHead,*smallTail,*bigHead,*bigTail,*cur,*next;        smallHead = smallTail = bigHead = bigTail = NULL;        cur = head;        while(cur)        {            next = cur->next;            if(cur->val
     
      next = next;                    if(smallTail)                    {                        smallTail->next = cur;                        cur->next = bigHead;                        smallTail = cur;                    }else                    {                        smallTail = smallHead = cur;                        cur->next = bigHead;                    }                                        }else                {                    if(smallTail)                    {                        smallTail = cur;                    }else                        smallTail = smallHead = cur;                }            }else            {               if(bigTail)                    bigTail = cur;                else                    bigTail = bigHead = cur;            }                        cur = next;                            }                return (smallHead?smallHead:bigHead);            }