TCS Coding Practice Question | HCF or GCD of 2 Numbers

Last Updated : 11 Jul, 2025

Given two numbers, the task is to find the HCF of two numbers using Command Line Arguments. GCD (Greatest Common Divisor) or HCF (Highest Common Factor) of two numbers is the largest number that divides both of them. Examples:

Input: n1 = 10, n2 = 20
Output: 10

Input: n1 = 100, n2 = 101
Output: 1

Approach:

Since the numbers are entered as Command line Arguments, there is no need for a dedicated input line
Extract the input numbers from the command line argument
This extracted numbers will be in String type.
Convert these numbers into integer type and store it in variables, say num1 and num2
Find the HCF of the numbers. An efficient solution is to use Euclidean algorithm which is the main algorithm used for this purpose. The idea is, GCD of two numbers doesn’t change if smaller number is subtracted from a bigger number.
Print or return the HCF

Program:

// C program to compute the HCF of two numbers
// using command line arguments

#include <stdio.h>
#include <stdlib.h> /* atoi */

// Function to compute the HCF of two numbers
int HCF(int a, int b)
{
    if (b == 0)
        return a;

    return HCF(b, a % b);
}

// Driver code
int main(int argc, char* argv[])
{

    int num1, num2;

    // Check if the length of args array is 1
    if (argc == 1)
        printf("No command line arguments found.\n");

    else {

        // Get the command line argument and
        // Convert it from string type to integer type
        // using function "atoi( argument)"
        num1 = atoi(argv[1]);
        num2 = atoi(argv[2]);

        // Find the HCF and print it
        printf("%d\n", HCF(num1, num2));
    }
    return 0;
}

Java

// Java program to compute the HCF of two numbers
// using command line arguments

class GFG {

    // Function to compute the HCF of two numbers
    static int HCF(int a, int b)
    {
        if (b == 0)
            return a;

        return HCF(b, a % b);
    }

    // Driver code
    public static void main(String[] args)
    {

        // Check if length of args array is
        // greater than 0
        if (args.length > 0) {

            // Get the command line argument and
            // Convert it from string type to integer type
            int num1 = Integer.parseInt(args[0]);
            int num2 = Integer.parseInt(args[1]);

            // Find the HCF
            int res = HCF(num1, num2);

            // Print the HCF
            System.out.println(res);
        }
        else
            System.out.println("No command line "
                               + "arguments found.");
    }
}