leetcode 86

先找到第一个大于等于target的数p，然后从这个数开始往后遍历链表，若比target小则放在p之前

ListNode* partition(ListNode* head, int x) {
        ListNode* dummy = new ListNode(-1);
        dummy->next = head;
        ListNode *p = dummy;
        ListNode *q = head;
        while(p->next&&p->next->val<x)p=p->next;
        q = p;
        while(q->next)
        {
            if(q->next->val<x)
            {
                ListNode* tem = q->next;
                q->next = tem->next;
                tem->next = p->next;
                p->next = tem;
                p = tem;
            }
            else q=q->next;
        }
        return dummy->next;
    }