solution.py

# Definition for singly-linked list.
from typing import Optional


class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

# Soution 1:


class Solution:
    def removeElements(self, head: Optional[ListNode], val: int) -> Optional[ListNode]:
        dummy = curr = ListNode(0)
        curr.next = head

        while curr.next:
            if curr.next.val == val:
                curr.next = curr.next.next
            else:
                curr = curr.next
        return dummy.next
# Solution 2:


# class Solution:
#     def removeElements(self, head: Optional[ListNode], val: int) -> Optional[ListNode]:
#         if not head:
#             return head
#         head.next = self.removeElements(head.next, val)
#         return head if head.val != val else head.next