题目描述

咦，为什么错了，嗯？怎么AC了。

算法1

(暴力枚举) $O(n)$

两条链表加起来的长度 应该是O（2n）吧

C++ 代码

class Solution {
public:
    ListNode* merge(ListNode* l1, ListNode* l2) {
        ListNode* s1 = l1,* s2 = l2,* dummy = new ListNode(-1);
        l1 = dummy;
        while(s1 && s2){
            if(s1->val <=s2->val) {
                dummy->next = s1;
                dummy = dummy->next ;
                s1 = s1->next;
            }
            else{
                dummy->next = s2;
                dummy = dummy->next ;
                s2 = s2->next;                
            }
        }
        if(!s1 &&!s2);
        else if(!s1) dummy->next = s2;
        else if(!s2) dummy->next = s1;


        return l1->next;
    }  
};