82. Remove Duplicates from Sorted List II

Description

Given 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.

Constraints

Approach

Links

• GeeksforGeeks

• Leetcode

• ProgramCreek

• YouTube

Examples

Example 1

Input: 1 -> 2 -> 3 -> 3 -> 4 -> 4 -> 5

Output: 1 -> 2 -> 5

Example 2

Solutions

Solution 1

/**
 * Time complexity : 
 * Space complexity : 
 */

/**
 * 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 deleteDuplicates(ListNode head) {
        if(head == null) return null;
        ListNode node = new ListNode(-1);
        node.next = head;

        ListNode curr = node;
        while(curr.next != null && curr.next.next != null) {
            if(curr.next.val == curr.next.next.val) {
                int value = curr.next.val;
                while(curr.next != null && curr.next.val == value) {
                    curr.next = curr.next.next;
                }
            } else {
                curr = curr.next;
            }
        }
        
        return node.next;
    }
}

Follow up