Introduction

The Remove Nth Node From End problem involves deleting the nth node from the end of a linked list.

The task is to:

  • find nth node from end
  • remove it safely
  • maintain linked list structure

Example:

Input:1 -> 2 -> 3 -> 4 -> 5
n = 2

Output:
1 -> 2 -> 3 -> 5

Explanation:

2nd node from end is: 4Remove node 4.
Updated list:
1 -> 2 -> 3 -> 5

This problem is one of the most important applications of:

Two Pointer Technique

Constraints

1 <= Number of Nodes <= 10^51 <= n <= Number of Nodes

Approach 1 : Brute Force (Using Length Calculation)

Explanations:

Explanation:

The idea is:

  • calculate linked list length
  • find node before target
  • remove nth node

Steps:

  1. Find total length.
  2. Locate node before target.
  3. Delete target node.

This approach works but:

  • requires two traversals

So two pointer solution is preferred.

Dry Run

Input:
1 -> 2 -> 3 -> 4 -> 5
n = 2

Length:
5

Target position:
5 - 2 = 3

Remove:
4

Output:
1 -> 2 -> 3 -> 5

Practice :

Complexity Analysis :

Time Complexity:- O(n)
Explanation :
Linked list is traversed twice.

Space Complexity:- O(1)
Explanation :
No extra space is used.

Approach 2 : Optimal Solution(Using Two Pointers)

Explanations:

Explanation:

This is the most optimized and interview-preferred solution.

The idea is:

  • move fast pointer n steps
  • move slow and fast together
  • slow reaches node before target

This removes node in:

  • single traversal

Dry Run

Input:1 -> 2 -> 3 -> 4 -> 5
n = 2

Fast moves:
2 steps ahead

Move both pointers.

Slow reaches:
3

Delete:
4

Output:
1 -> 2 -> 3 -> 5

Practice :

Complexity Analysis :

Time Complexity:- O(n)
Explanation :
Linked list is traversed once.

Space Complexity:- O(1)
Explanation :
No extra space is used.

Why This Problem is Important

This problem builds the foundation for:

  • Two Pointer Technique
  • Linked List deletion
  • Pointer traversal
  • Single-pass algorithms
  • Efficient node handling

Real-World Applications

Linked list deletion concepts are used in:

  • Task scheduling
  • Cache management
  • Undo systems
  • Memory management
  • Dynamic data structures

Common Beginner Mistakes

  • Incorrect fast pointer movement
  • NULL pointer errors
  • Forgetting dummy node
  • Wrong node deletion
  • Infinite loops

Interview Tip

Interviewers often expect:

  • Two Pointer optimization
  • single traversal solution
  • proper pointer handling
  • edge case handling

Always explain:

  • why fast moves first
  • how slow reaches target position

Related Questions

  • Middle of Linked List
  • Linked List Cycle
  • Reverse Linked List
  • Merge Two Sorted Lists
  • Delete Node in Linked List

Final Takeaway

The Remove Nth Node From End problem is one of the most important Two Pointer linked list problems.

It teaches:

  • pointer traversal
  • linked list deletion
  • efficient node handling
  • single-pass algorithms

Understanding this problem builds a strong foundation for:

  • advanced linked list problems
  • pointer-based algorithms
  • interview-level data structure questions.