[leetcode]Copy List with Random Pointer

Copy List with Random Pointer 

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中的原题

算法思路：

遍历原list的每一个节点，对每一个节点生成一个copy节点，插到原节点的后面。完成next的拷贝

第二遍扫描，对每一个原节点的random节点，其copy节点的random应该为原节点random.next。完成random的拷贝

第三遍扫描，将copy list取下来。

【注意】：分解原list和copy list时候，要完整的把原list给组装起来。不能破坏原list的结构。

public class Solution {
    public RandomListNode copyRandomList(RandomListNode head) {
            if(head == null) return null;
            RandomListNode node = head;
            while(node != null){
                RandomListNode tem = new RandomListNode(node.label);
                tem.next = node.next;
                node.next = tem;
                node = node.next.next;
            }
            node = head;
            while(node != null){
                RandomListNode next = node.next;
                if(node.random != null)
                    next.random = node.random.next;
                node = node.next.next;
            }
            RandomListNode hhead = new RandomListNode(0);
            RandomListNode pointer = hhead;
            node = head;
            while(node != null){
                pointer.next = node.next;
                pointer = node.next;
                node.next = node.next.next;
                node = node.next;
            }
            return hhead.next;
        }
}