來自：https://blog.csdn.net/futureflyme/article/details/72780789

package interview;
import java.util.*;

//定義節點結構
class Node {
    int data;
    Node next = null;
    Node(int data) {
        this.data = data;
    }
}

public  class TestDuplicate {
    public static void main(String[] args) {

        int [] arr=new int[] {5,4,4,3,3,2,1};

        //定義一個for迴圈,每次在連結串列頭部插入元素,從而建立一個連結串列
        Node head1=null;
        for(int i=0;i<arr.length;i++){
            Node node=new Node(arr[i]);
            node.next=head1;
            head1=node;
        }
        System.out.println("原來的連結串列： ");
        Node temp1=head1;
        while(temp1!=null){
            System.out.print(temp1.data+" ");
            temp1=temp1.next;
        }
        System.out.println();

        Node head2 = deleteDuplication(head1);
        System.out.println("去重後的連結串列： ");
        Node temp2=head2;
        while(temp2!=null){
            System.out.print(temp2.data+" ");
            temp2=temp2.next;
        }
    }
    //這個方法不是真正的連結串列去重
    public static Node deleteDuplication(Node phead) {
        HashSet<Integer> set = new HashSet<Integer>();
        Node tempNode = phead;
        while (tempNode != null) {
            set.add(tempNode.data);
            tempNode = tempNode.next;
        }
        //for迴圈,每次在連結串列的尾部插入元素,從而建立一個連結串列
        Node head=null;
        Node temp = head;
        for (Integer num : set) {
            Node node = new Node(num);
            if(head==null){
                head=node;
            }else{
                temp.next=node;
            }
            temp=node;
        }
        return head;
    }
}