Remove Duplicates from Sorted List - LeetCode

Remove Duplicates from Sorted List

  Total Accepted: 9360  Total Submissions: 27531 My Submissions

Given a sorted linked list, delete all duplicates such that each element appear only once.

For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if(head == null)
        return head;
        ListNode current =  head;
        ListNode past = new ListNode(999);
        int c = 9999;
        while(current != null){
            if(past.val == current.val ){
                past.next = current.next;
                current = current.next;
            }
            else{
            past = current;
            current = current.next;
            }
        }
        return head;
    }
}