Find the Sum of Last N nodes of the Linked List

Slug: find-the-sum-of-last-n-nodes-of-the-linked-list

Difficulty: Easy

Id: 700594

Topic Tags: Linked List, Data Structures

Company Tags: None

Summary

Given a linked list and an integer n, find the sum of the last n nodes in the linked list. This problem is related to data structures and manipulation of linked lists.

Detailed Explanation

To solve this problem, we will traverse the linked list from the end to the beginning. We keep track of the sum of the last n nodes as we iterate through the linked list.

Here's a step-by-step breakdown of the solution:

1. Initialize a variable sum to 0.
2. Traverse the linked list from the end to the beginning using a pointer p.
3. As you traverse, keep track of the sum of the last n nodes by adding each node's value to sum.
4. Return sum.

The time complexity for this solution is O(L), where L is the length of the linked list, since we need to traverse the entire list. The space complexity is O(1) as we only use a constant amount of space to store the sum.

Here's an ASCII art diagram illustrating the traversal:

    5 -> 4 -> 3 -> 2 -> 1
      ^
      p (starts at the end)

Optimized Solutions

Java