Multiply Polinoms

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _12.SumMultPolinoms
{
    class Program
    {
        // Extend the program to support also subtraction and multiplication of polynomials.

        static decimal[] addArraysOfDigits(decimal[] arr1, decimal[] arr2)
        {
            int maxLen = arr1.Length > arr2.Length ? arr1.Length : arr2.Length;

            decimal[] tempArr = new decimal[maxLen];
            decimal[] sum = new decimal[maxLen];

            if (arr1.Length > arr2.Length)
            {
                for (int i = 0; i < maxLen; i++)
                {
                    if (i < arr2.Length)
                    {
                        tempArr[i] = arr2[i];
                    }
                    else
                    {
                        tempArr[i] = 0;
                    }
                }

                for (int i = 0; i < sum.Length; i++)
                {
                    if (i < arr1.Length)
                    {
                        sum[i] = (arr1[i] + tempArr[i]);
                    }
                }
            }
            else
            {
                for (int i = 0; i < maxLen; i++)
                {
                    if (i < arr1.Length)
                    {
                        tempArr[i] = arr1[i];
                    }
                    else
                    {
                        tempArr[i] = 0;
                    }
                }

                for (int i = 0; i < sum.Length; i++)
                {
                    if (i < arr2.Length)
                    {
                        sum[i] = (arr2[i] + tempArr[i]);
                    }
                }
            }

            return sum;
        }

        static decimal[] substractArraysOfDigits(decimal[] arr1, decimal[] arr2)
        {
            int len = arr1.Length > arr2.Length ? arr1.Length : arr2.Length;
            int shortLen = arr1.Length < arr2.Length ? arr1.Length : arr2.Length;

            decimal[] sum = new decimal[len];

            for (int i = 0; i < shortLen; i++)
            {
                sum[i] = (arr1[i] - arr2[i]);
            }

            if (arr2.Length > arr1.Length)
            {
                for (int i = shortLen; i < len; i++)
                {
                    sum[i] = -arr2[i];
                }
            }
            else
            {
                for (int i = shortLen; i < len; i++)
                {
                    sum[i] = arr1[i];
                }
            }

            return sum;
        }

        static decimal[] multiplyArraysOfDigits(decimal[] arr1, decimal[] arr2)
        {

            int len = arr1.Length + arr2.Length;

            decimal[] sum = new decimal[len];

            for (int i = 0; i < arr1.Length; i++)
            {
                for (int j = 0; j < arr2.Length; j++)
                {
                    if (arr1[i] != 0 && arr2[j] != 0)
                    {
                        sum[i + j] += arr1[i] * arr2[j];
                    }
                }
            }

            return sum;
        }

        static void PrintPolinomial(decimal[] polinomial)
        {
            bool begining = false;
            for (int i = polinomial.Length - 1; i >= 0; i--)
            {
                if (polinomial[i] > 0)
                {
                    if (begining == false)
                    {
                        Console.Write("{1}x^{0}", i, polinomial[i]);
                        begining = true;
                    }
                    else
                    {
                        Console.Write(" +{1}x^{0}", i, polinomial[i]);
                    }
                }
                else if (polinomial[i] < 0)
                {
                    Console.Write(" {1}x^{0}", i, polinomial[i]);
                    if (begining == false)
                    {
                        begining = true;
                    }
                }
            }
            Console.WriteLine();
            Console.WriteLine();
        }

        static void Main(string[] args)
        {
            decimal[] arr1 = { 0, 2, 3, 0 };
            Console.WriteLine("Array 1: " + string.Join("\t", arr1));
            decimal[] arr2 = { 0, 4, 0 ,2 };
            Console.WriteLine("Array 2: " + string.Join("\t", arr2));
            Console.WriteLine();


            // add
            Console.WriteLine("Add\n");
            decimal[] sum = addArraysOfDigits(arr1, arr2);
            Console.WriteLine("Array 3: " + string.Join("\t", sum));
            PrintPolinomial(sum);

            // substract
            Console.WriteLine("Substracting...\n");
            decimal[] substract = substractArraysOfDigits(arr1, arr2);
            Console.WriteLine("Array 4: " + string.Join("\t", substract));
            PrintPolinomial(substract);

            decimal[] substract2 = substractArraysOfDigits(arr2, arr1);
            Console.WriteLine("Array 5: " + string.Join("\t", substract2));
            PrintPolinomial(substract2);

            // multiply
            Console.WriteLine("Multiply...\n");
            decimal[] multiply = multiplyArraysOfDigits(arr1, arr2);
            Console.WriteLine("Array 6: " + string.Join("\t", multiply));
            PrintPolinomial(multiply);

            decimal[] multiply2 = multiplyArraysOfDigits(arr2, arr1);
            Console.WriteLine("Array 7: " + string.Join("\t", multiply2));
            PrintPolinomial(multiply2);

        }
    }
}