[LeetCode]Copy List with Random Pointer

Map<RandomListNode, RandomListNode> m = new HashMap<RandomListNode, RandomListNode>();
//保存已经copy的部分

public RandomListNode copyRandomList(RandomListNode head) {
RandomListNode rList = null;
if(head == null) return rList;
else {
rList = new RandomListNode(head.label);
m.put(head, rList);
if(m.get(head.next) != null){
rList.next = m.get(head.next);
}else
rList.next = copyRandomList(head.next);
if(m.get(head.random) != null) {
rList.random = m.get(head.random);
}else
rList.random = copyRandomList(head.random);
}

return rList;
}