Q138 复制带随机指针的链表

输入：
{"$id":"1","next":{"$id":"2","next":null,"random":{"$ref":"2"},"val":2},"random":{"$ref":"2"},"val":1}

解释：
节点 1 的值是 1，它的下一个指针和随机指针都指向节点 2 。
节点 2 的值是 2，它的下一个指针指向 null，随机指针指向它自己。

/*
// Definition for a Node.
class Node {
    public int val;
    public Node next;
    public Node random;

    public Node() {}

    public Node(int _val,Node _next,Node _random) {
        val = _val;
        next = _next;
        random = _random;
    }
};
*/
class Solution {
    public Node copyRandomList(Node head) {
        if (head == null)
            return null;

        LinkedList<Node> list = new LinkedList<>();
        HashMap<Node, Node> map = new HashMap<>();
        Node node = head;

        while (node != null) {
            Node temp = new Node(node.val, node.next, node.random);
            map.put(node, temp);
            node = node.next;
        }

        for (Node n : map.keySet()) {
            Node temp = map.get(n);
            temp.next = map.get(n.next);
            temp.random = map.get(n.random);
        }

        return map.get(head);
    }
}

class Solution {
    public Node copyRandomList(Node head) {
        if (head == null)
            return null;

        Node node = head;
        while (node != null) {
            Node temp = new Node(node.val, node.next, node.random);
            node.next = temp;
            node = temp.next;
        }

        node = head;
        Node copyHead = head.next;
        while (node != null) {
            Node temp = node.next;
            if (temp.random != null) {
                temp.random = temp.random.next;
            }
            node = node.next.next;
        }

        node = head;
        while (node != null) {
            Node temp = node.next;
            node.next = temp.next;
            node = node.next;
            if (node != null)
                temp.next = node.next;
            else
                temp.next = null;
        }

        return copyHead;
    }
}