0083 - Remove Duplicates from Sorted List

0083 - Remove Duplicates from Sorted List

Given the head of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well.

Examples

Input: head = [1,1,2] Output: [1,2]

Input: head = [1,1,2,3,3] Output: [1,2,3]

Constraints

The number of nodes in the list is in the range [0, 300]. -100 <= Node.val <= 100 The list is guaranteed to be sorted in ascending order

Java Solution

/**
 * 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 || head.next == null) return head;

        ListNode previous = head;
        ListNode pointer = head.next;

        while(pointer != null) {
            if(pointer.val == previous.val) {
                previous.next = pointer.next;
                pointer = pointer.next;
            } else {
                previous = pointer;
                pointer = pointer.next;
            }
        }
        return head;
    }
}