复杂链表的复制（不使用额外空间）

 思路：比如说原链表是ABCD。则先复制结点A' B' C' D'，分别连接在ABCD后面。然后遍历ABCD，得知每个原结点的random指向。那么复制结点的random指向原结点random的后一个。(A---C，则A'----C后面的C') 再次遍历链表，将所有原结点跨个相连，将复制结点跨个相连。返回复制结点的第一个即可。

/*
public class RandomListNode {
    int label;
    RandomListNode next = null;
    RandomListNode random = null;

    RandomListNode(int label) {
        this.label = label;
    }
}
*/
public class Solution {
        public RandomListNode Clone(RandomListNode pHead){
            if(pHead == null) return null;
            CloneNode(pHead);
            CloneRandom(pHead);
            return SeperateListNode(pHead);
        }
        
        public void CloneNode(RandomListNode pHead){
            RandomListNode cNode = null;
            while(pHead != null){
                cNode = new RandomListNode(pHead.label);
                cNode.next = pHead.next;
                pHead.next = cNode;
                pHead = pHead.next.next;
            }
        }
        
        public void CloneRandom(RandomListNode pHead){
            RandomListNode cNode = null;
            while(pHead != null){
                cNode = pHead.next;
                if(pHead.random != null){
                     cNode.random = pHead.random.next;
                }
                pHead = cNode.next;
            }
        }
        
        public RandomListNode SeperateListNode(RandomListNode pHead){
            RandomListNode result = pHead.next;
            while(pHead != null && pHead.next != null){
                RandomListNode cCurr = pHead.next;
                if(pHead.next != null){
                    pHead.next = pHead.next.next;
                }
                if(cCurr != null && cCurr.next != null){
                    cCurr.next = cCurr.next.next;
                }
                pHead = pHead.next;
                cCurr = cCurr.next;
            }
            return result;
        }
}