LeetCode 23. 合并K个排序链表

class Solution {
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        auto l=new ListNode(-1);
        auto cur=l;
        auto p=l1,q=l2;
        while(p&&q){
            if(p->val>q->val){
                cur->next=q;
                q=q->next;
            }
                
            else{
                cur->next=p;
                p=p->next;
            }
                
            cur=cur->next;
        }
        cur->next=p?p:q;
        return l->next;
    }
    ListNode* mergeKLists(vector<ListNode*>& lists) {
        if(!lists.size())return NULL;
        if(lists.size()==1)return lists[0];
        int mid=lists.size()/2;
        auto left=vector<ListNode*>(lists.begin(),lists.begin()+mid);
        auto right=vector<ListNode*>(lists.begin()+mid,lists.end());
        auto l1=mergeKLists(left);
        auto l2=mergeKLists(right);
        return mergeTwoLists(l1,l2);
    }
};