Copy_List_with_Random_Pointer.java

/**
 * 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) {
        
        if(head == null) return null;
        
        for(RandomListNode cur = head;cur != null;){
            
            RandomListNode node = new RandomListNode(cur.label);
            node.next = cur.next;
            cur.next = node;
            cur = node.next;
        }
        
        for(RandomListNode cur = head;cur != null;){
            if(cur.random != null)cur.next.random = cur.random.next;
            cur = cur.next.next;
        }
        
        RandomListNode result = new RandomListNode(-1);
        
        for(RandomListNode tmp = result,cur = head;cur != null;){
            
            tmp.next = cur.next;
            cur.next = cur.next.next;
            tmp = tmp.next;
            cur = cur.next;
        }
        
        return result.next;
    }
}