Prime factors C# Exercise - C# Programming Course

using System;  // Import the System namespace to use basic classes like Console

class Program  // Define the main class of the program
{
    static void Main()  // The entry point of the program
    {
        // Ask the user to enter a number
        Console.Write("Enter a number: ");  // Display prompt for the number input
        int number = int.Parse(Console.ReadLine());  // Read the input as an integer

        int originalNumber = number;  // Store the original number for display later
        string result = originalNumber + " = ";  // Start the result string

        // Check for divisibility by 2 first (for efficiency)
        while (number % 2 == 0)  // While the number is divisible by 2
        {
            result += "2 · ";  // Append '2' to the result string
            number /= 2;  // Divide the number by 2
        }

        // Now check for odd factors starting from 3
        for (int i = 3; i <= Math.Sqrt(number); i += 2)  // Only check odd numbers (i += 2)
        {
            while (number % i == 0)  // While the number is divisible by 'i'
            {
                result += i + " · ";  // Append the factor 'i' to the result string
                number /= i;  // Divide the number by 'i'
            }
        }

        // If the remaining number is greater than 2, it must be prime
        if (number > 2)
        {
            result += number + " · ";  // Append the last prime factor
        }

        // To remove the final " · " from the result string
        result = result.Substring(0, result.Length - 2);  // Remove last two characters

        // Display the result
        Console.WriteLine(result);  // Print the prime factorization of the number
    }
}