138. 复制带随机指针的链表

1.遍历链表里的节点，并存在hashmap中
2.再遍历一遍，调整map中节点的next、random指针
3.返回map
/*
// Definition for a Node.
class Node {
public:
    int val;
    Node* next;
    Node* random;
    
    Node(int _val) {
        val = _val;
        next = NULL;
        random = NULL;
    }
};
*/

class Solution {
public:
    Node* copyRandomList(Node* head) {
        if(head == NULL) return NULL;
        Node *tmp = head;
        unordered_map<Node*, Node*>mp;
        while(tmp!=NULL){
            mp[tmp] = new Node(tmp->val);
            tmp = tmp->next;
        }
        tmp = head;
        while(tmp!=NULL){
            mp[tmp]->next = mp[tmp->next];
            mp[tmp]->random = mp[tmp->random];
            tmp = tmp->next;
        }
        return mp[head];
    }
};