复制带随机指针的链表

/*
// 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;
    }
}
*/
//第一种方法使用HashMap方法方法
class Solution {
    public Node copyRandomList(Node head) {
        if(head==null){
            return null;
        }
        //将节点复制到到键值对中
        Node node=head;
        Map<Node,Node> map=new HashMap<>(); 
        while(node!=null){
            Node clone=new Node(node.val);
            map.put(node,clone);
            node=node.next;
        }
        node=head;
        //复制随机域
        while(node!=null){
            map.get(node).next=map.get(node.next); //随机立减
            map.get(node).random=map.get(node.random);
            node=node.next;
        }
        return map.get(head);
    }
}

class Solution {
    public Node copyRandomList(Node head) {
        if(head==null){
            return null;
        }
        //原地复制节点
        Node current=head;
        while(current!=null){
            Node clone=new Node(current.val);
            Node temp= current.next;
            clone.next=current.next;
            current.next=clone;
            current=temp;
        }
        //处理随机节点，要注意画图和校验
        current=head;
        while(current!=null){
            if(current.random!=null){
                 current.next.random=current.random.next;
            }
            current=current.next.next;
        }
        ///将两个链表拆开
        Node newHead=new Node(-1);
        newHead=head.next;
        current=head;
        while(current.next!=null){
         Node temp=current.next;
         current.next=current.next.next;
         current=temp;
        }
        return newHead;
    }
}