138. 随机链表的复制 - 力扣（LeetCode） (opens new window)

hash映射

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

常规

class Solution {
    public Node copyRandomList(Node head) {
        if(head == null) return null;
        Node cur = head;
        //复制各节点并紧接插入
        while(cur != null){
            Node tmp = new Node(cur.val);
            tmp.next = cur.next;
            cur.next = tmp;
            cur = tmp.next;
        }
        //构建新节点的random指向
        cur = head;
        while(cur != null){
            if(cur.random != null){
                cur.next.random = cur.random.next;
            }
            cur = cur.next.next;
        }
        //拆分两个链表
        cur = head.next;
        Node pre = head, res = head.next;
        while(cur.next != null){
            pre.next = pre.next.next;
            cur.next = cur.next.next;
            pre = pre.next;
            cur = cur.next;
        }
        pre.next = null;
        return res;
    }