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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.

我的想法

在循环建立新链表的时候，用一个hashmap存入所有新建的点。再用一个循环遍历原链表，补充新链表的random结点。但是这样只能用于结点没有重复的val

class Solution {
       public Node copyRandomList(Node head) {
           if(head == null) {
               return head;        }        HashMap
   
     map = new HashMap<>();        Node res = new Node(head.val, null, null);        Node resHead = res;        map.put(resHead.val, resHead);        Node temp = head.next;        while(temp != null) {
               Node node = new Node(temp.val, null, null);            map.put(node.val, node);            resHead.next = node;            resHead = resHead.next;            temp = temp.next;        }        resHead = res;        while(head != null) {
               if(head.random != null) {
                   resHead.random = map.get(head.random.val);            }            head = head.next;            resHead = resHead.next;        }        return res;    }}
   

解答

为了解决重复val的问题，hashmap的key应该是老的结点

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