Leetcode 19: Remove Nth Node From End of List - python

removeNthEndNode.py

def removeNthFromEnd(head,n):
# O(2n) || O(1)
    count = 0
    cur = head

    while cur:
        count += 1
        cur = cur.next

    m = count - n

    if m == 0:
        # when m is 0, need to remove the head by making the next node head
        return head.next

    cur = head
    count = 1

    while cur:
        if count == m:
            # when cur node is the node before n (count == m), remove the nth node 
            cur.next = cur.next.next
            break

        count += 1
        cur = cur.next

    return head

# fast and slow pointers : O(n) || O(1)
    fast = slow = head

    for _ in range(n):
        fast = fast.next

    if not fast:
        return head.next

    while fast.next:
        fast, slow = fast.next, slow.next

    slow.next = slow.next.next

    return head