Introduction to Linked Lists and Interview Challenges in Go

Welcome back! As we focus on mastering interview-oriented problems using linked lists in Go, we'll explore practical, algorithmic challenges you may encounter during technical interviews.

Consider the following real-life problem: You’re tasked with organizing a digital library where some books have been accidentally duplicated. Your goal is to identify and remove these redundant entries to ensure each title in your catalog is unique.

A naive approach would be to browse each book and compare it with every other title in a nested loop fashion. Just like in a large library, this approach would be inefficient, with a time complexity of $O(n^2)$. As the dataset grows, the time taken increases exponentially with each additional book — similar to searching an entire library for duplicates each time a new book is added.

To address the issues with the naive approach, we use a more strategic method similar to maintaining a checklist: marking off each book as we encounter it. In Go, we achieve this by using a map to record unique titles, thereby reducing our time complexity to $O(n)$.

type ListNode struct {
    Value int
    Next  *ListNode
}

func RemoveDuplicates(head *ListNode) *ListNode {
    if head == nil || head.Next == nil {
        return head
    }

    seenBooks := make(map[int]bool)
    current := head
    seenBooks[current.Value] = true

    for current.Next != nil {
        if seenBooks[current.Next.Value] {
            current.Next = current.Next.Next
        } else {
            seenBooks[current.Next.Value] = true
            current = current.Next
        }
    }
    return head
}

In this solution, we use a Go map to track previously seen books. As we traverse the linked list, if we encounter a book already present in the map, we remove it by adjusting pointers. Otherwise, we add it to the map. This approach efficiently ensures all titles are unique.