LeetCode 刷题【138. 随机链表的复制】

138. 随机链表的复制

自己做

解：哈希表

/*
// Definition for a Node.
class Node {
    int val;
    Node next;
    Node random;

    public Node(int val) {
        this.val = val;
        this.next = null;
        this.random = null;
    }
}
*/

class Solution {
    public Node copyRandomList(Node head) {
        Node p = head;
        Node res = new Node(0);
        Node q = res;
        List<Node> list = new ArrayList();
        Map<Node, Integer> hash1 = new HashMap();
        int i = 0;

        //根据next复制链表
        while(p != null){
            q.next = new Node(p.val);
            q = q.next;

            hash1.put(p, i);
            list.add(q);
            
            p = p.next;
            i++;
        }

        //建立random
        p = head;
        q = res.next;

        while(p != null){
            if(p.random != null)
                q.random = list.get(hash1.get(p.random));
            else
                q.random = null;

            p = p.next;
            q = q.next;
        }


        return res.next;
    }
}