0019 Remove Nth Node From End of List.py

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def removeNthFromEnd(self, head: Optional[ListNode], n: int) -> Optional[ListNode]:
        slow = fast = head
        for i in range(n): 
            fast = fast.next
        if not fast: return slow.next

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