83. Remove Duplicates from Sorted List

Problem

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

Example 1:

Input: 1->1->2
Output: 1->2

Example 2:

Input: 1->1->2->3->3
Output: 1->2->3

Solution (Java)

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

Solution (Javascript)

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var deleteDuplicates = function(head) {
  var now = head;
  while (now) {
    if (now.next && now.next.val === now.val) {
      now.next = now.next.next;
    } else {
      now = now.next;
    }
  }
  return head;
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(1).