Copy List with Random Pointer --- LeetCode

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.

解题思路：1.遍历链表，在旧节点后面插入同样的新节点，copy旧节点的label和random

            2.遍历链表，将新节点的random值指向旧random节点的下一节点（即为新random节点）

            3.将新旧链表分开，恢复旧链表结构，输出新链表

/**
 * 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) {
         RandomListNode copyHead=null;
           RandomListNode point=head;
      if(head==null){
      return null;
      }
           while(point!=null){
         RandomListNode copyNode=new RandomListNode(point.label); 
         copyNode.next=point.next;
         copyNode.random=point.random;
         point.next=copyNode;
         point=point.next.next;          
           }
           
           point=head;
           while(point!=null){
          if(point.next.random!=null){
          point.next.random=point.random.next; 
          }
               point=point.next.next;
           }
           
           point=head;
           RandomListNode tmp=new RandomListNode(0);
           copyHead=tmp;
           while(point!=null){ 
         tmp.next=point.next; 
         point.next=point.next.next; 
         point=point.next;                  
         tmp=tmp.next;          
           }
           tmp=copyHead;
           copyHead=copyHead.next; 
           tmp.next=null;
           return copyHead;  
    }
}