Remove n’th node from end of list#

1Given linked list: 1->2->3->4->5, and n = 2.
2After removing the second node from the end, the linked list becomes 1->2->3->5.

 1class ListNode(object):
 2    def __init__(self, x):
 3        self.val = x
 4        self.next = None
 5
 6
 7class Solution:
 8    def removeNthFromEnd(self, head, n):
 9        if not head:
10            return
11        fast = slow = head
12        for _ in range(n):
13            if not fast.next:
14                raise Exception("less than n nodes found")
15            fast = fast.next
16        if not fast:
17            return head.next
18        while fast.next:
19            fast = fast.next
20            slow = slow.next
21        slow.next = slow.next.next
22        return head