Problem Copy List with Random Pointer

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Problem Description:

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.

 

 Solution:

 1     public RandomListNode copyRandomList(RandomListNode head) { 2        Map<RandomListNode, RandomListNode> map = new HashMap<RandomListNode, RandomListNode>(); 3  4         if (head == null) return null; 5  6         RandomListNode q = head; 7         RandomListNode p = null; 8         while (q != null ) { 9             p = new RandomListNode(q.label);10             map.put(q, p);11             q = q.next;12         } 13 14         q = head;15         RandomListNode root = map.get(head);16         while (q != null) {17             p = map.get(q);18             p.next = map.get(q.next);19             p.random = map.get(q.random);20             q = q.next;21         }22 23         return root;24     }