【leetcode 138. 复制带随机指针的链表】解题报告

方法一:递归

    unordered_map<Node*,Node*> dict;
    Node* copyRandomList(Node* head) {
        if (!head) return head;
        if (dict.count(head)) return dict[head];
        dict[head]=new Node(head->val, nullptr, nullptr);
        dict[head]->next=copyRandomList(head->next);
        dict[head]->random=copyRandomList(head->random);
        return dict[head];
    }

方法二:非递归

    Node* copyRandomList(Node* head)
    {
        if (!head) return head;
        unordered_map<Node*,Node*> m;
        Node *p=head;
        while(p)    // make a copy of nodes
        {
            m[p]=new Node(p->val,nullptr,nullptr);
            p=p->next;
        }
        p=head;
        while(p)    // link everyone and fill the random field
        {
            m[p]->next=m[p->next];
            m[p]->random=m[p->random];
            p=p->next;
        }
        return m[head];
    }