//Programmer: Jiamiao Zeng

//Date: Start - Nov. 15, 2024; End - Nov. 21, 2024

//Project: Greatest Common Factor

/*Description: A program that takes 2 user input numbers and calculates the greatest

common factor of the 2*/

​

using System;

​

class calcResult //creates class named calcResult with 2 variables, result and smallNum

{

    public int result; //variables are stored as integers

    public int smallNum;

}

​

public class Program

{

    static int readNum() //method for reading the two user inputs, returns an integer

    {

        int i; //declares integer for TryParse method

        startRead: //marks start of taking user input

            string input = Console.ReadLine(); //declares string input

        if (int.TryParse(input, out i) == true && Convert.ToInt32(input) > 0)

        {

            ///converts the input into an int if convertable and the number is bigger than 0

            int num = Convert.ToInt32(input);

            return num; //return the int

        }

        else

        {

            Console.WriteLine("Please enter a positive integer.");

            goto startRead; //retakes input if the value is invalid

        }

    }

​

    static calcResult calculation(int num1, int num2) //method that takes 2 integers and returns variables according to the calcResult class

    {

        int bigNum; //declares the 2 integers for calculation

        int smallNum;

        if (num1 > num2)

        { //set bigger number is num1 if it is bigger than num2

            bigNum = num1;

            smallNum = num2;

        }

        else

        { //if num1 is smaller or equal to num2, set num1 to the smaller number

            smallNum = num1;

            bigNum = num2;

        }

​

        var outcome = new calcResult //declare variable to be returned, containing 2 possible variables

        {

            result = bigNum % smallNum, //calculates the remainder of bigNum divided by smallNum to be returned

            smallNum = smallNum //set value of smallNum to that of the smaller number

        };

        return outcome; //both variables are returned

    }

​

    public static void Main()

    {

        Console.WriteLine("Greatest Common Factor" + "\n" + "Please enter two numbers you want to find the Greatest Common Factor (GCF)");

        int num1 = readNum(); //calls the read input method twice to generate 2 integers based on user input

        int num2 = readNum();

        var result = calculation(num1, num2); //calls the method that does the number conparison and calculation, creating result object that can be either the remainder or the smaller num

        while (result.result != 0) //when remainder is not 0, loop the code below

        {

            result = calculation(result.result, result.smallNum); //calculate result, setting the parameter of the method to be the smaller number and the remainder of the last calculation 

        }

​

        Console.WriteLine("The greatest common factor is " + result.smallNum); //breaks out of the loop when result is 0 and display the smaller number in the calculation

    }

}