remove_duplicates_from_sorted_list.py

from typing import Optional

# Definition for singly-linked list.
class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next


class Solution:
    """
    Task:
    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.
    """
    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
        if head is None:
            return head

        cur = head
        while cur.next != None:
            if cur.next.val == cur.val:
                cur.next = cur.next.next
            else:
                cur = cur.next
        return head