[leetcode]Copy List with Random Pointer

1. 第一次遍历深度克隆链表费random属性，并使用map记录一一对应的链表节点

2. 第二次遍历，根据map记录的节点关系，补全random引用

/**
 * 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;
        }
        Map<RandomListNode, RandomListNode> map = new HashMap<RandomListNode, RandomListNode>();
        RandomListNode p = head;
        RandomListNode headNew = new RandomListNode(head.label);
        RandomListNode pNew = headNew;
        map.put(p, pNew);
        while (p != null){
            RandomListNode next = p.next;
            if(next == null){
                break;
            }
            RandomListNode nextNew = new RandomListNode(next.label);
            pNew.next = nextNew;
            p = p.next;
            map.put(next, nextNew);
            pNew = pNew.next;
        }
        p = head;
        pNew = headNew;
        while (p != null){
            RandomListNode rand = p.random;
            RandomListNode randNew = map.get(rand);
            pNew.random = randNew;
            p = p.next;
            pNew = pNew.next;
        }
        return headNew;
    }

}