移除重复节点
编写代码,移除未排序链表中的重复节点。保留最开始出现的节点。
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]
思路
将出现的重复数字添加到set
中,判断是否重复出现
解答
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode removeDuplicateNodes(ListNode head) {
Set<Integer> set = new HashSet<>();
if (head == null) return null;
ListNode pre = null, newHead = head;
while (head != null) {
ListNode next = head.next;
if (!set.contains(head.val)) {
set.add(head.val);
pre = head;
head = next;
} else {
pre.next = next;
head = next;
}
}
return newHead;
}
}