[JAVA/LeetCode] Top 100 Liked Question: 138. Copy List with Random Pointer

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/**
 *
 * @author HEESOO
 *
 */
/*
// 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 head;
        
        HashMap<Node, Node> map=new HashMap<>();
        Node p=head;
        while(p!=null){ // 새 노드 생성
            map.put(p, new Node(p.val));
            p=p.next;
        }
        
        p=head;
        while(p!=null){ // 새 노드들에 next, random 연결
            map.get(p).next=map.get(p.next);
            map.get(p).random=map.get(p.random);
            p=p.next;
        }
        
        return map.get(head);
    }
}