138. Copy List with Random Pointer

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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.

剑指offer 26题

分三步：

　　第一步：复制结点，复制的结点放在待复制的结点后，依然组成一个单链表 
　　第二步：串接随机指针 
　　第三步：将原单链表与复制链表拆开 

public class Solution {
    public RandomListNode copyRandomList(RandomListNode head) {
        if(head==null) return head;
        copyNode(head);
        connectNode(head);
        return splitNode(head);
        
    }
    
    
    public void copyNode(RandomListNode head){
        RandomListNode node = head;
        while(node !=null){
            RandomListNode copyNode = new RandomListNode(node.label);
            copyNode.next = node.next;
            node.next = copyNode;
            node = copyNode.next;
        }
    }
    
    public void connectNode(RandomListNode head){
        RandomListNode node = head;
        while(node != null){
            if(node.random!=null)
                node.next.random = node.random.next;
            node = node.next.next;
        }
        
    }
    
    public RandomListNode splitNode(RandomListNode head){
        RandomListNode copyhead = head.next;
        RandomListNode node = head;
        RandomListNode copynode ;
        
        while(node != null){
            copynode = node.next;
            node.next = copynode.next;
        
            if(node.next!= null)
                copynode.next = node.next.next;
    
            node = node.next;
        }
        return copyhead;
    }
    
}