LeetCode 82. Remove Duplicates from Sorted List II

Question

Given the head of a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. Return the linked list sorted as well.

https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/

• Solution1

class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode pre = dummy, cur = head;
        while(cur != null && cur.next != null){
            if(cur.val == cur.next.val){
                int temp = cur.val;
                while(cur != null && temp == cur.val) cur = cur.next;
                pre.next = cur;
            } else {
                pre = pre.next;
                cur = cur.next;
            }
        }
        return dummy.next;
    }
}

Complexity:

Time complexity: O(n)

Space complexity: O(1)