what' wrong with following code

Question

what's wrong with following code? only pass 4/11 test case

Input: {1,2,2,2} Output: {1,2,1,1} Expected: {1,2,2,2}

I test it offline, but it is ok.

The main idea is following picture, 1) Create all nodes in copy linked list using next pointers. 3) Store the node and its next pointer mappings of original linked list. 3) Change next pointer of all nodes in original linked list to point to the corresponding node in copy linked list.

Thank!

public class Solution {
public RandomListNode copyRandomList(RandomListNode head) {
       if(head == null){
           return null;
       }
       HashMap<RandomListNode,RandomListNode> map = new HashMap<RandomListNode,RandomListNode>();

       RandomListNode root =new RandomListNode(head.label);
       RandomListNode res = root;
       RandomListNode copy = head;
       root.next =null;
       //create group2
        RandomListNode temp = null;
       while(head.next!=null){
           head =head.next;
           temp =new RandomListNode(head.label);
           temp.next =null;
           root.next = temp;
           root =root.next;
       }

       // map group 1 to group2
       head = copy;
       root = res;
       while(head!=null){
           map.put(head, res);
           head = head.next;
           root = root.next;
       }

       head = copy;
       root = res;
       //copy random pointer
       while(head!=null){
           root.random=map.get(head.random); 
           head = head.next;
           root = root.next;               
       }

       return res;
}

}