remove-linked-list-elements.py

# Time:  O(n)
# Space: O(1)
#
# 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
#
# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    # @param {ListNode} head
    # @param {integer} val
    # @return {ListNode}
    def removeElements(self, head, val):
        dummy = ListNode(float("-inf"))
        dummy.next = head
        prev, curr = dummy, dummy.next
        
        while curr:
            if curr.val == val:
                prev.next = curr.next
            else:
                prev = curr
            
            curr = curr.next
        
        return dummy.next