Listing Factors of Numbers in C# - Math Programming for Kids

What are Factors? | Maths Explanation for C# Kids

Factors are the complete set of integers that will divide a particular number without remainder.
Take 36 as an example, it's complete set are:

1, 2, 3, 4, 6, 9, 12, 18, and 36.

Other than prime numbers, every other number has at least one factor - not considering 1 as factor.
Where there is just one factor, then this factor is the square root of the number in question;
In this guide, we'll explore the math behind factors-of-numbers and walk through how to code a C# algorithm for listing factors in a simple and fun way.

Code Logic for Factorising Numbers in C# - Fun Maths Exercise

Actually, we've been doing factors over the last two demonstrations (lessons).

We can implement a C# algorithm for factorising a number by simply checking for our factors using the square-root of number range.
We'll start from 1 (which is always a factor).
For each found factor, we'll get the corresponding complementary factor by dividing the number (whose factors we are trying to find), by the found factor.
This Math activity and C# script help primary school students understand factorization by listing all factors of a number.

Create a new C# class file; Project, Add Class.
Call it ListFactors.

Type out the adjoining C# code for listing factors.

Note: You can comment out the C# code for the main class from the previous lesson if you have been following.

So! C# Fun Practice Exercise - List Factors

As a fun practice exercise, feel free to try out your own different numbers, and see how the C# code lists the factors of those numbers.

C# Code for List Factors class.

using System;
using System.Collections.Generic;

namespace Arithmetic
{
    class ListFactors
    {
        private List<int> found_factors;
        private int find_my_factors;
        private int sqrt_range; // Use this range for our loop

        public ListFactors(int candidate)
        {
            found_factors = new List<int>();
            find_my_factors = candidate;
            sqrt_range = (int)Math.Ceiling(Math.Sqrt(find_my_factors));
        }

        /**
         * Does the main job of finding the requested factors.
         * @return - array list of integers
         */
        public List<int> doBusiness()
        {
            /* Loop through 1 to 'find_my_factors' and test for divisibility. */
            for (int i = 1; i < sqrt_range; i++)
            {
                if ((find_my_factors % i) == 0)
                {
                    found_factors.Add(i);
                    /* Get the complementing factor by dividing 'find_my_factor' by variable i. */
                    found_factors.Add(find_my_factors / i);
                }
            }

            // Sort the array in ascending order; Not entirely necessary.
            found_factors.Sort();

            return found_factors;
        }
    }
}

C# Code for List Factors - Main class.

using System;
using System.Collections.Generic;

namespace Arithmetic
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Welcome to our demonstration sequels");
            Console.WriteLine("Hope you enjoy (and follow) the lessons.");
            Console.WriteLine("\r\n");

            /*
            * List Prime Numbers.
             */
            int candidate = 48;
            List<int> answer;

            ListFactors factors = new ListFactors(candidate);
            answer = factors.doBusiness();

            Console.WriteLine("Factors of " + candidate + " are:");
            Console.WriteLine(String.Join(", ", answer));

        }
    }
}

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