LeetCode122|删除排序链表中的重复元素II

示例 1:

输入: 1->2->3->3->4->4->5
输出: 1->2->5
示例 2:

输入: 1->1->1->2->3
输出: 2->3

import java.util.*;
import java.util.stream.Collectors;

public class DeleteDuplicatesTest3 {
    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(4);
        ListNode l6 = new ListNode(4);
        ListNode l7 = new ListNode(5);
        l1.next = l2;
        l2.next = l3;
        l3.next = l4;
        l4.next = l5;
        l5.next = l6;
        l6.next = l7;
        ListNode listNode = deleteDuplicates(l1);
        System.out.println("listNode = " + listNode);
    }

    public static ListNode deleteDuplicates(ListNode head) {
        if (head == null) {
            return null;
        }
        if (head.next == null) {
            return head;
        }
        HashMap<Integer, Integer> hashMap = new LinkedHashMap<>();
        ListNode dummyNode = head;
        while (dummyNode != null) {
            hashMap.put(dummyNode.val, hashMap.getOrDefault(dummyNode.val, 0) + 1);
            dummyNode = dummyNode.next;
        }
        List<Integer> list = hashMap.entrySet().stream().filter(Objects::nonNull).filter(x -> x.getValue() == 1)
                .map(Map.Entry::getKey).collect(Collectors.toList());
        ListNode newHead = new ListNode(-1);
        int size = list.size();
        ListNode tempNode = newHead;
        for (int i = 0; i < size; i++) {
            tempNode.next = new ListNode(list.get(i));
            tempNode = tempNode.next;
        }
        return newHead.next;
    }


}