LeetCode142|移除重复节点

示例1:

 输入：[1, 2, 3, 3, 2, 1]
 输出：[1, 2, 3]
示例2:

 输入：[1, 1, 1, 1, 2]
 输出：[1, 2]
提示：

链表长度在[0, 20000]范围内。
链表元素在[0, 20000]范围内。

 

import java.util.LinkedHashSet;
import java.util.Set;

public class RemoveDuplicateNodesTest {
    public static void main(String[] args) {
        ListNode l1 = new ListNode(1);
        ListNode l2 = new ListNode(2);
        ListNode l3 = new ListNode(3);
        ListNode l4 = new ListNode(3);
        ListNode l5 = new ListNode(2);
        ListNode l6 = new ListNode(1);
        l1.next = l2;
        l2.next = l3;
        l3.next = l4;
        l4.next = l5;
        l5.next = l6;
        ListNode listNode = removeDuplicateNodes(l1);
        System.out.println("listNode = " + listNode);

    }

    public static ListNode removeDuplicateNodes(ListNode head) {
        if (head == null || head.next == null) {
            return head;
        }
        Set<Integer> hashSet = new LinkedHashSet<>();
        while (head != null) {
            hashSet.add(head.val);
            head = head.next;
        }
        ListNode dummyNode = new ListNode(-1);
        ListNode tempNode = dummyNode;
        for (Integer num : hashSet) {
            ListNode listNode = new ListNode(num);
            tempNode.next = listNode;
            tempNode = tempNode.next;
        }
        return dummyNode.next;
    }
}