复制含有随机指针的节点的链表

什么意思，单链表中只有一个next指针，而这里的多了一个rand指针，rand指针是随机任意节点的指针。

 public static class Node {
        private int val;
        private Node next;
        private Node rand;

        public Node(int data) {
            this.val = data;
        }
    }

两种方法，第一种是用哈希表，第二种使用有限几个变量。

方法一：

    public static Node copyListWithRand1(Node head) {
        //key表示存储当前链表的节点，value表示新的节点
        HashMap<Node, Node> map = new HashMap<Node, Node>();
        Node cur = head;
        while (cur != null) {
            map.put(cur, new Node(cur.value));
            cur = cur.next;
        }
        cur = head;
        while (cur != null) {
            //cur 老
            //map.get(cur)新
            map.get(cur).next = map.get(cur.next);
            map.get(cur).rand = map.get(cur.rand);
            cur = cur.next;
        }
        return map.get(head);
    }

方法二：

public static Node copyListWithRand2(Node head) {
        if(head == null) {
            return null;
        }
        Node cur = head;
        Node next = null;
        while(cur != null) {
            next = cur.next;
            cur.next = new Node(cur.value);
            cur.next.next = next;
            cur = next;
        }
        cur = head;
        Node curCopy = null;
        while (cur != null) {
            next = cur.next.next;
            curCopy = cur.next;
            curCopy.rand = cur.rand != null ? cur.rand.next : null;
            cur = next;

        }
        Node res = head.next;
        cur = head;
        while(cur != null) {
            next = cur.next.next;
            curCopy = cur.next;
            cur.next = next;
            curCopy.next = next != null ? next.next : null;
            cur = next;
        }
        return res;
    }