LeetCode 82:删除排序链表中的重复元素 II

题目：

方法一：

方法二：

代码示例

package com.zy.leetcode.LeetCode_82;

/**
 * @Author: zy
 * @Date: 2024-12-26-10:51
 * @Description:
 * .删除排序链表中的重复元素 II
 */
public class ListNode_82 {

    private int val;

    private ListNode_82 next;

    public ListNode_82(int val, ListNode_82 next) {
        this.val = val;
        this.next = next;
    }

    public ListNode_82() {
    }

    public ListNode_82(int val) {
        this.val = val;
    }

    /**
     * 构造一个方法，输入一个数组，然后初始化链表
     */
    public static ListNode_82 initListNode(int[] arr) {
        ListNode_82 dummy = new ListNode_82(0);
        ListNode_82 cur = dummy;
        for (int num : arr) {
            cur.next = new ListNode_82(num);
            cur = cur.next;
        }
        return dummy.next;
    }

    private void print(ListNode_82 node) {
        while (node != null) {
            System.out.print(node.val + " -> ");
            node = node.next;
        }
    }

    /**
     * 递归
     *
     * @param node
     * @return
     */
    private ListNode_82 deleteDuplicateNode(ListNode_82 node) {
        //临界条件判断
        if (node == null || node.next == null) {
            return node;
        }
        if (node.val == node.next.val) {
            // 找到第一个与下一个值不等的节点
            while (node.next != null && node.val == node.next.val) {
                node.next = node.next.next;
            }
            return deleteDuplicateNode(node.next);
        } else {
            node.next = deleteDuplicateNode(node.next);
            return node;
        }
    }

    private ListNode_82 deleteDuplicateNode2(ListNode_82 node) {
        //临界条件判断
        if (node == null || node.next == null) {
            return node;
        }
        ListNode_82 s = new ListNode_82(-1, node);
        ListNode_82 p1 = s;
        ListNode_82 p2, p3;

        while ((p2 = p1.next) != null && (p3 = p2.next) != null) {
            if (p2.val == p3.val) {
                while ((p3 = p3.next) != null && (p2.val == p3.val)) {
                    //不做操作
                }
                //找到了不相等的位置
                p1.next = p3;
            } else {
                p1 = p1.next;
            }
        }
        return s.next;
    }

    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 3, 4, 4, 5};
        ListNode_82 head = initListNode(arr);
        System.out.print("原始链表：");
        head.print(head);
        System.out.println();

        ListNode_82 result = new ListNode_82().deleteDuplicateNode(head);
        System.out.print("删除后链表1：");
        result.print(result);

        System.out.println();

        ListNode_82 result1 = new ListNode_82().deleteDuplicateNode(head);
        System.out.print("删除后链表2：");
        result.print(result1);

    }
}