Polynomials

using System;
using System.Collections.Generic;
//Write a method that adds two polynomials. Represent them as arrays of their coefficients as in the example below:
//        x2 + 5 = 1x2 + 0x + 5
//Extend the program to support also subtraction and multiplication of polynomials.
class Program
{
    static void Main()
    {
        //7x^3 + 4x^2 -3x + 2
        decimal[] pol1 = {2,-3,4,7};
        //1x2 + 0x + 5
        decimal[] pol2 = { 5, 0, 1 };
        //swap arrays to set shortest array at first position
        SetShortestArrayFirst(ref pol1, ref pol2);

        decimal[] result = new decimal[pol2.Length];

        //add
        result = AddPolynomials(pol1, pol2);
        PrintResult(result);
        Array.Clear(result,0,result.Length);

        //substract
        result = SubstractPolynomials(pol1, pol2);
        PrintResult(result);

        //multiplay
        decimal[] multiplayResult = new decimal[pol1.Length + pol2.Length];
        multiplayResult = MultiplayPolynomials(pol1, pol2);
        PrintResult(multiplayResult);
    }

    private static decimal[] MultiplayPolynomials(decimal[] pol1, decimal[] pol2)
    {
        decimal[] result = new decimal[pol1.Length + pol2.Length];
        int pos;
        for (int i = 0; i < pol1.Length; i++)
        {
            for (int j = 0; j < pol2.Length; j++)
            {
                pos = i + j;
                result[pos] += (pol1[i] * pol2[j]);
            }
        }
        return result;
    }

    private static decimal[] SubstractPolynomials(decimal[] pol1, decimal[] pol2)
    {
        decimal[] result = new decimal[pol2.Length];

        for (int i = 0; i < pol2.Length; i++)
        {
            if (i < pol1.Length)
            {
                result[i] = pol2[i] - pol1[i];
            }
            else
            {
                result[i] = pol2[i];
            }
        }
        return result;
    }

    private static void PrintResult(decimal[] result)
    {
        for (int i = result.Length-1; i >= 0; i--)
        {
            if (i > 1)
            {
                if (i == result.Length - 1)
                {
                    Console.Write("{0}x^{1}", result[i], i);
                }
                else
                {
                    if (result[i] > 0)
                    {
                        Console.Write("+{0}x^{1}", result[i], i);
                    }
                    else
                    {
                        Console.Write("{0}x^{1}", result[i], i);
                    }
                }
            }
            else if (i == 1)
            {
                if (result[i] > 0)
                {
                    Console.Write("+{0}x",result[i]);
                }
                else
                {
                    Console.Write("{0}x",result[i]);
                }
            }
            else if (i == 0)
            {
                if (result[i] > 0)
                {
                    Console.Write("+{0}", result[i]);
                }
                else
                {
                    Console.Write("{0}", result[i]);
                }
            }
        }
        Console.WriteLine();
    }

    private static decimal[] AddPolynomials(decimal[] pol1, decimal[] pol2)
    {
        decimal[] result = new decimal[pol2.Length];

        for (int i = 0; i < pol2.Length; i++)
        {
            if (i < pol1.Length)
            {
                result[i] = pol1[i] + pol2[i];
            }
            else
            {
                result[i] = pol2[i];
            }
        }
        return result;
    }

    private static void SetShortestArrayFirst(ref decimal[] pol1,ref decimal[] pol2)
    {

        if (pol1.Length > pol2.Length)
        {
            //swap arrays
            decimal[] temp = (decimal[])pol1.Clone();
            pol1 = new decimal[pol2.Length];
            Array.Copy(pol2, pol1, pol2.Length);
            pol2 = new decimal[temp.Length];
            Array.Copy(temp, pol2, temp.Length);
        }
    }


}