/*
 * @lc app=leetcode id=138 lang=java
 *
 * [138] Copy List with Random Pointer
 */

// @lc code=start
/*
// Definition for a Node.
class Node {
    int val;
    Node next;
    Node random;

    public Node(int val) {
        this.val = val;
        this.next = null;
        this.random = null;
    }
}
*/

class Solution {
    public Node copyRandomList(Node head) {
        if(head == null) {
            return null;
        }
        Map<Node, Node> ref = new HashMap<>();
        Node cur = head;
        while(cur != null) {
            Node cp = new Node(cur.val);
            ref.put(cur, cp);
            cur = cur.next;
        }
        cur = head;
        while(cur != null) {
            Node nd = ref.get(cur);
            nd.next = ref.get(cur.next);
            nd.random = ref.get(cur.random);
            cur = cur.next;
        }
        return ref.get(head);
    }
}
// @lc code=end