How hard is LeetCode 19. Remove Nth Node From End of List?

LeetCode 19. Remove Nth Node From End of List is rated Medium on LeetCode.

What is the time complexity of LeetCode 19. Remove Nth Node From End of List?

The Python solution on this page runs in O(n), where n is the length of the linked list.

What is the space complexity of LeetCode 19. Remove Nth Node From End of List?

The Python solution on this page uses O(1) auxiliary space.

What topics does LeetCode 19. Remove Nth Node From End of List cover?

LeetCode 19. Remove Nth Node From End of List is tagged Linked List and Two Pointers on LeetCode.

Remove Nth Node From End of List — LeetCode 19 Python Solution

MediumLinked ListTwo Pointers

Problem: #19
Pattern: Linked List
Reading time: 3 min
Source: leetcode.com

The problem

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

Example

Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]

Python solution

Python

# 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]:
        dummy = ListNode(next=head)
        fast = slow = dummy
        for _ in range(n):
            fast = fast.next
        while fast.next:
            slow, fast = slow.next, fast.next
        slow.next = slow.next.next
        return dummy.next

Complexity

Measure	Complexity
Time	O(n), where n is the length of the linked list
Space	O(1) auxiliary

Pattern: Linked List

Rewire pointers in place, with a dummy head and a saved next to keep it safe. LeetCode 19. Remove Nth Node From End of List is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Linked List.

The linked list guide has the Python template for the pattern and the 75 LeetCode problems that use it.

On study lists

This problem is on Blind 75, NeetCode 150 and Top Interview 150.

Frequently asked questions

How hard is LeetCode 19. Remove Nth Node From End of List?: LeetCode 19. Remove Nth Node From End of List is rated Medium on LeetCode.
What is the time complexity of LeetCode 19. Remove Nth Node From End of List?: The Python solution on this page runs in O(n), where n is the length of the linked list.
What is the space complexity of LeetCode 19. Remove Nth Node From End of List?: The Python solution on this page uses O(1) auxiliary space.
What topics does LeetCode 19. Remove Nth Node From End of List cover?: LeetCode 19. Remove Nth Node From End of List is tagged Linked List and Two Pointers on LeetCode.