Write a program to calculate GCD or HCF of two numbers.

GCD or HCF

The HCF or GCD of two numbers is the largest number which can fully divide both numbers. For example, the GCD or HCF of 20 and 30 is 10.

Program

using System;

namespace ProgrammingQuestion
{
 class Program
 {
   static void Main(string[] args)
   {
     //Variable Declaration
     string firstNumberVal, secondNumberVal;
     int firstNumber, secondNumber, GCD = 1, minNumber;

     //User Input
     Console.Write("Enter First Number:");
     firstNumberVal = Console.ReadLine();
     firstNumber = Convert.ToInt32(firstNumberVal);
     Console.Write("Enter Second Number:");
     secondNumberVal = Console.ReadLine();
     secondNumber = Convert.ToInt32(secondNumberVal);
     
     //GCD or HCF Logic
     if(firstNumber < secondNumber)
     {
       minNumber = firstNumber;
     }
     else
     {
       minNumber = secondNumber;
     }
     for (int i = 1; i <= minNumber/2; i++)
     {
       if (firstNumber % i == 0 && secondNumber % i == 0)
       {
         GCD = i;
       }
     }
     
     //Print Result
     Console.WriteLine($"GCD of {firstNumber} and {secondNumber} is {GCD}.");
     
     Console.Read();
   }
 }
}

Output

Enter First Number:30
Enter Second Number:40
GCD of 30 and 40 is 10.