19. Remove Nth Node From End of List

Medium

Given a linked list, remove the n-th node from the end of list and return its head.

😇 Solution

O(n)

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

class Solution:
    def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
        
        dummy = ListNode(-1)
        dummy.next = head
        
        node = head
        l = 0
        while(node!=None):
            l += 1
            node = node.next
        
        l = l-n
        node = dummy
        while(l > 0):
            l -= 1
            node = node.next
            
        node.next = node.next.next
        
        return dummy.next