【链表】无序链表中移除重复项

import java.util.HashSet;
import java.util.Set;

public class Main {

    // 从无序链表中删除重复项
    public Node removeDup(Node node) {

        if (node == null || node.next == null || node.next.next == null) {
            return node;
        }

        Set<Integer> set = new HashSet<Integer>();

        Node pre = node;
        Node curr = node.next;

        while (curr != null) {
            if (set.contains(curr.data)) {
                pre.next = curr.next;
            } else {
                set.add(curr.data);
                pre = curr;
            }

            curr = curr.next;
        }

        return node;
    }

    public Node createListNodes() {
        Node node7 = new Node(7, null);
        Node node6 = new Node(5, node7);
        Node node5 = new Node(4, node6);
        Node node4 = new Node(5, node5);
        Node node3 = new Node(1, node4);
        Node node2 = new Node(3, node3);
        Node node1 = new Node(1, node2);
        Node head = new Node(0, node1); // head pointer

        return head;
    }

    public static void main(String[] args) {
        Main main = new Main();
        Node node = main.removeDup(main.createListNodes());

        if (node != null) {
            node = node.next;
            while (node != null) {
                System.out.println(node.data);
                node = node.next;
            }
        }
    }
}