Remove Linked List Elements

Remove all elements from a linked list of integers that have value val.

Example Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6 Return: 1 --> 2 --> 3 --> 4 --> 5

URL: https://leetcode.com/problems/remove-linked-list-elements/

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

class Solution(object):
    def removeElements(self, head, val):
        """
        :type head: ListNode
        :type val: int
        :rtype: ListNode
        """
        if head == None:
            return head
        elif head != None and head.next == None:
            if head.val == val:
                return None
            else:
                return head
        else:
            dummy = ListNode(0)
            dummy.next = head
            prev = dummy

            while head != None:
                if head.val == val:
                    prev.next = head.next
                    head = prev
                prev = head
                head = head.next

            return dummy.next