🎓 HackerRank Practice: Student Marks Manager using C# Lists

Working with Lists is one of the most common exercises in coding challenges. Lists in C# are dynamic collections that allow adding, removing, and inserting elements easily. Let’s solve a simple HackerRank-style problem step by step.

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📌 Problem Statement: Student Marks Manager

You are given student marks. Perform operations using a List<int>.

Input
5
10 20 30 40 50
3
Add 60
Remove 20
Insert 25 2

Output
10 25 30 40 50 60

Explanation

• Start: [10, 20, 30, 40, 50]
• Add 60 → [10, 20, 30, 40, 50, 60]
• Remove 20 → [10, 30, 40, 50, 60]
• Insert 25 at index 2 → [10, 25, 30, 40, 50, 60]

✅ This tests:

• Index-based access
• Add / Remove operations
• Insert at a given index

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🛠️ Solution in C#

using System;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        // Input: number of students
        int n = int.Parse(Console.ReadLine());

        // Input: student marks
        string[] input = Console.ReadLine().Split(' ');
        List<int> marks = new List<int>();

        for (int i = 0; i < n; i++)
            marks.Add(int.Parse(input[i]));

        // Input: number of operations
        int noOfOperations = int.Parse(Console.ReadLine());

        // Perform operations
        for (int i = 0; i < noOfOperations; i++)
        {
            string[] command = Console.ReadLine().Split();
            string operation = command[0];
            int value = int.Parse(command[1]);

            if (operation == "Add")
            {
                marks.Add(value);
            }
            else if (operation == "Remove")
            {
                marks.Remove(value);
            }
            else if (operation == "Insert")
            {
                int index = int.Parse(command[2]);
                marks.Insert(index, value);
            }
        }

        // Output final list
        Console.WriteLine(string.Join(' ', marks));
    }
}

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🔎 Walkthrough

1. Reading Input
   • First line → number of students n.
   • Second line → list of marks.
   • Third line → number of operations.
   • Following lines → commands (Add, Remove, Insert).
2. Using List<int>
   • Add(value) → appends an item.
   • Remove(value) → removes the first occurrence of an item.
   • Insert(index, value) → inserts at a specific position.
3. Output
   • After performing all operations, we print the final list using string.Join(' ', marks).

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🚀 Key Learnings

• List<T> is flexible compared to arrays.
• You can directly use Add, Remove, and Insert methods.
• Indexing in C# Lists starts from 0.

This type of problem is great for practicing basic data structures and input/output handling in coding contests.