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83. 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.

Example 1:

img

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

Example 2:

img

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.
/**
 * 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 cur = head;
        while(cur.next != null){
            if (cur.next.val == cur.val){
                cur.next = cur.next.next;
            }else{
                cur = cur.next;
            }
        }

        return head;

    }
}

// TC: O(n)
// SC: O(1)