copy list with random pointer 解题报告

public class  {
    
     * @param head: The head of linked list with a random pointer.
     * @return: A new head of a deep copy of the list.
     */
    public RandomListNode copyRandomList(RandomListNode head) {
        //insert new node to list
        if(head == null){
            return null;
        }
        if(head.next == null){
            return new RandomListNode(head.label);
        }
        
        RandomListNode start = head;
        while(head != null){
            RandomListNode node = new RandomListNode(head.label);
            node.next = head.next;
            head.next = node;
            head = node.next;
        }
        
        //copy random pointer
        head = start;
        while(head != null){
            if(head.random != null){
                head.next.random = head.random.next;
            }
            head = head.next.next;
        }
        
        //break
        head = start;
        RandomListNode head2 = head.next;
        RandomListNode start2 = head2;
        while(head2.next != null){
            head.next = head2.next;
            head2.next = head.next.next;
            head = head.next;
            head2 = head2.next;
            // System.out.println("lalala");
        }
        head.next = null;
        return start2;
    }
}