java复制多向链表的方法

多向链表结构如

（视频教程推荐：java课程）

public class Node{
    public int value;
    public Node next;
    public Node rand;
    public Node(int data){
        this.value = data;
       }
}

方法一：使用HashMap结构

public class CopyFromMultiNode {
    public static void main(String[] args){
        int[] array = {12,3,4,5,6,77,6,54,56,6,7,87,15,15,15};
        //数组转Node
        Node head = array2node(array);
        Node help = head;
        System.out.print("处理前     ");
        while(help != null){
            System.out.print(help.value + " ");
            help = help.next;
        }
 
        //使用HashMap结构
        Node res = copyFromRand1(head);
        System.out.println();
        System.out.print("处理后结果：");
        while(res != null){
            System.out.print(res.value+" ");
            res = res.next;
        }
    }
 
    //使用HashMap结构
    public static Node copyFromRand1(Node head){
        Node cur = head;
        HashMap<Node, Node> map = new HashMap<>();
        while(cur != null){
            map.put(cur, new Node(cur.value));
            cur = cur.next;
        }
        cur = head;
        while(cur != null){
            map.get(cur).next = map.get(cur.next);
            map.get(cur).rand = map.get(cur.rand);
            cur = cur.next;
        }
        return map.get(head);
    }
 
    //数组转Node功能，供测试使用
    public static Node array2node(int[] array){
        Node head = new Node(array[0]);
        Node cur = head;
        for(int i=1; i<array.length; i++){
            cur.next = new Node(array[i]);
            cur = cur.next;
        }
        return head;
    }
 
    //基础node节点结构
    public static class Node{
        public int value;
        public Node next;
        public Node rand;
        public Node(int data){
            this.value = data;
        }
    }
}

2、使用几个有效变量方法，无需其他结构

    //使用几个有效变量方法
    //替换方法一的copyFromRand1方法
    public static Node copyFromRand2(Node head){
        Node next = null;
        Node cur = head;
        //1 -> 2 -> 3 -> 4 ==> 1 -> 1` -> 2 -> 2` -> 3 -> 3` -> 4 -> 4
        //完成链表拼接
        while(cur != null){
            next = cur.next;
            cur.next = new Node(cur.value);
            cur.next.next = next;
            cur = next;
        }
        cur = head;
        Node curCopy = null;
        //添加Node的rand值
        while(cur != null){
            next = cur.next.next;
             curCopy = cur.next.next;
             curCopy = cur.rand != null? cur.rand.next: null;
            cur = next;
        }
        Node res = head.next;
        cur = head;
        //拆分
        //  1 -> 1` -> 2 -> 2` -> 3 -> 3` -> 4 -> 4
        //   ==>  1 -> 2 -> 3 -> 4  和 1`-> 2`-> 3`-> 4`
        while(cur != null){
            next = cur.next.next;
            curCopy = cur.next;
            cur.next = next;
            curCopy.next = next != null ? next.next:null;
            cur = next;
        }
        return res;
    }

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