一样的代码，现在提交通过不了！！！
提示不能修改原链表
把代码修改一下就可以过了！

C++ 代码

 ```
 class Solution {
public:
    ListNode *copyRandomList(ListNode *head) {

        for(auto p = head; p;) {
            auto np = new ListNode(p->val);
            auto next = p->next;
            p->next = np;
            np->next = next;
            p = next;
        }

        for(auto p=head; p;p=p->next->next){
            if(p->random)
                p->next->random = p->random->next;


        }

        auto dummy = new ListNode(-1);
        auto cur = dummy;
        for(auto p= head; p;) {
        auto pre = p;
        cur->next = p->next;
        cur = cur->next;
        p = p->next->next;
        pre->next = p;
        }
        return dummy->next;
    }
};
 ```

算法2

(暴力枚举) $O(n^2)$

blablabla

时间复杂度分析：blablabla

C++ 代码

blablabla