Copy List with Random Pointer

1. Title

Copy List with Random Pointer

2. Http address

https://leetcode.com/problems/copy-list-with-random-pointer/

3. The question

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.

Return a deep copy of the list.

 4. My code(AC)

class RandomListNode {
    int label;
    RandomListNode next,random;
    public RandomListNode(int x)
    {
            this.label = x;
    }

}

//Accpeted
    public static RandomListNode copyRandomList(RandomListNode head)
    {
            Map<RandomListNode,RandomListNode> mapH = new HashMap<RandomListNode,RandomListNode>();
            RandomListNode re,    q,end;
            RandomListNode p = head;
            re = null;
            end = null;
            while( p != null )
            {
                q = new RandomListNode(p.label);
                if( end == null)
                {
                    re = q;
                    end = q;
                }else{
                    end.next = q;
                    end = q;
                }
                mapH.put(p,q);
                p = p.next;
            }

            p = head;
            q = re;
            while( p != null && q != null) {
                if( p.random != null )
                {
                    q.random = mapH.get(p.random);
                
                }else{
                    q.random = null;
                }
                p = p.next;
                q = q.next;
            }
        return re;

    }