Problem: 2487. 从链表中移除节点

👨‍🏫 参考题解

💖 递归解法

/*** Definition for singly-linked list.* public class ListNode {*     int val;*     ListNode next;*     ListNode() {}*     ListNode(int val) { this.val = val; }*     ListNode(int val, ListNode next) { this.val = val; this.next = next; }* }*/
class Solution {public ListNode removeNodes(ListNode head) {if(head.next == null){return head;// 递归出口}head.next = removeNodes(head.next);// 递归处理右侧的链表// 右侧的链表 经过处理后的头结点肯定是 右侧最大的节点if(head.next != null && head.val < head.next.val)// 如果当前节点小于右侧最大的节点{return head.next;// 删除当前节点}else{return head;// 不处理}}
}

💖 单调栈

/*** Definition for singly-linked list.* public class ListNode {*     int val;*     ListNode next;*     ListNode() {}*     ListNode(int val) { this.val = val; }*     ListNode(int val, ListNode next) { this.val = val; this.next = next; }* }*/
class Solution {public ListNode removeNodes(ListNode head){LinkedList<ListNode> stack = new LinkedList<>();while (head != null){stack.push(head);head = head.next;}while (!stack.isEmpty()){if (head == null || stack.peek().val >= head.val){stack.peek().next = head;head = stack.peek();}stack.pop();}return head;}
}