package com.zerroi.leetcode.Three25;

public class DeleteDuplicates {
    public static void main(String[] args) {
//        ListNode head = constructLinkedList(new int[]{1, 2, 3, 3, 4, 4, 5});
        ListNode head = constructLinkedList(new int[]{1, 1});
        SolutionSecond solutionSecond = new SolutionSecond();
        ListNode res = solutionSecond.deleteDuplicates(head);
        while (res != null) {
            System.out.println("res.val = " + res.val);
            res = res.next;
        }
    }

    public static ListNode constructLinkedList(int[] nums) {
        if (nums == null || nums.length == 0) {
            return null;
        }

        ListNode dummy = new ListNode(); // 创建一个虚拟头节点
        ListNode current = dummy;

        for (int num : nums) {
            current.next = new ListNode(num);
            current = current.next;
        }

        return dummy.next; // 返回真正的头节点
    }
}

class SolutionSecond {
    public ListNode deleteDuplicates(ListNode head) {
        if (head == null || head.next == null) return head;
        ListNode dummy = new ListNode(-1);
        dummy.next = head;
//        pre指针为cur的前驱节点
        ListNode pre = dummy;
//        cur为当前节点
        ListNode cur = head;
        while (cur != null && cur.next != null) {
//            如果出现当前节点的值等于其下一节点值，要一直循环找到不相等的
            if (cur.val == cur.next.val) {
                int duplicate = cur.val;
                while (cur != null && cur.val == duplicate) {
                    cur = cur.next;
                }
                pre.next = cur;
            } else {
                pre = pre.next;
                cur = cur.next;
            }
        }
        return dummy.next;
    }
}