Leetcode-Copy List with Random Pointer

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.

Solution:

/**
 * Definition for singly-linked list with a random pointer.
 * class RandomListNode {
 *     int label;
 *     RandomListNode next, random;
 *     RandomListNode(int x) { this.label = x; }
 * };
 */
public class Solution {
    public RandomListNode copyRandomList(RandomListNode head) {
        Map<RandomListNode,RandomListNode> map = new HashMap<RandomListNode,RandomListNode>();
        if (head==null) return null;

        RandomListNode head2 = new RandomListNode(head.label);
        map.put(head,head2);
        RandomListNode cur = head2;

        while (head!=null){
            RandomListNode rand1 = head.random;
            if (rand1!=null && map.containsKey(rand1)){
                cur.random = map.get(rand1);
            } else if (rand1!=null) {
                RandomListNode rand2 = new RandomListNode(rand1.label);
                map.put(rand1,rand2);
                cur.random = rand2;
            }

            if (head.next==null){
                cur.next=null;
            } else {
                RandomListNode next = head.next;
                if (map.containsKey(next))
                    cur.next = map.get(next);
                else {
                    RandomListNode next2 = new RandomListNode(next.label);
                    cur.next = next2;
                    map.put(next,next2);
                }
            }

            head = head.next;
            cur = cur.next;
        }

        return head2;        
    }
}