题意
拷贝一个结点的所有子结点，与前面有一题一样的解法
class Solution {
Map<Node, Node> copied = new HashMap<>();
public Node copyRandomList(Node head) {
if (head == null) {
return null;
}
if (copied.containsKey(head)) {
return copied.get(head);
}
Node temp = new Node();
copied.put(head, temp);
temp.val = head.val;
temp.next = copyRandomList(head.next);
temp.random = copyRandomList(head.random);
return temp;
}
}