算法练习(9)-复杂带随机指针的单链表

class Node {
    int val;
    Node next;
    Node random;

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

public Node copyRandomList(Node head) {
        if (head==null){
            return null;
        }
        Node h = head;
        Map<Node,Node> map = new HashMap<>();
        Node newHead = new Node(head.val);
        Node curr = newHead;
        //第一轮，复制节点，random挂空，同时记录处理过的老节点与新节点的映射关系
        while(head!=null){
            if (head.next!=null){
                Node newNext = new Node(head.next.val);
                curr.next = newNext;
            }
            map.put(head,curr);
            head = head.next;
            curr = curr.next;
        }
        head = h;
        //第二轮，处理random指向，通过map映射，查到random指向的新节点
        while(head!=null){
            Node newNode = map.get(head);
            if (head.random!=null){
                newNode.random = map.get(head.random);
            }
            head = head.next;
        }
        return newHead;
    }

public Node copyRandomList(Node head) {
        if (head==null){
            return head;
        }
        Node curr = head;
        //复制自身，挂在身后
        while(curr!=null){
            Node newNode = new Node(curr.val);
            newNode.next = curr.next;
            curr.next = newNode;
            curr = curr.next.next;
        }

        //复制random
        curr = head;
        while(curr!=null){
            if (curr.random!=null){
                curr.next.random = curr.random.next;
            }
            curr = curr.next.next;
        }

        //分离链表
        curr = head;
        Node newHead = head.next;

        while(curr!=null){
            Node newCurr = curr.next;
            curr.next = curr.next.next;
            if (newCurr.next!=null){
                newCurr.next = newCurr.next.next;
            }
            curr = curr.next;
        }

        return newHead;
    }