TCS Coding Practice Question | Checking Prime Number

Given a number N, the task is to check if N is a Prime Number or not using Command Line Arguments.

Examples:

Input: N = 7
Output: Yes

Input: N = 15
Output: No

Approach:



  • Since the number is entered as Command line Argument, there is no need for a dedicated input line
  • Extract the input number from the command line argument
  • This extracted number will be in String type.
  • Convert this number into integer type and store it in a variable, say N
  • Now loop through the numbers from 2 to N/2+1, using a variable say i.
    In each iteration,

    • Check if i divide N completely (i.e. if it is a factor of N).
    • If yes, then N is not a prime number.
    • If no, then N is a prime number.
  • After the loop has ended, it is found out that N is prime or not.

Note: Please note that 1 is not checked in this scenarios because 1 is niether prime nor composite.

Program:

C

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// C program to find
// the Prime Numbers from 1 to N
// using command line arguments
  
#include <stdio.h>
  
#include <stdlib.h> /* atoi */
  
// Function to check if x is prime
int isPrime(int x)
{
    int i;
  
    // Loop to check if x has any factor
    // other than 1 and x itself
    for (i = 2; i < x / 2 + 1; i++) {
        if (x % i == 0) {
            // Since i is a factor of x
            // x is not prime
            return 0;
        }
    }
  
    // x is prime
    return 1;
}
  
// Driver code
int main(int argc, char* argv[])
{
  
    int n;
  
    // 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)"
        n = atoi(argv[1]);
  
        // Check if n is prime
        if (isPrime(n) == 1)
            printf("Yes\n");
        else
            printf("No\n");
    }
  
    return 0;
}

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Java

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// Java program to reverse a string
// using command line arguments
  
class GFG {
  
    // Function to check if x is prime
    public static int isPrime(int x)
    {
        int i;
  
        // Loop to check if x has any factor
        // other than 1 and x itself
        for (i = 2; i < x / 2 + 1; i++) {
            if (x % i == 0) {
                // Since i is a factor of x
                // x is not prime
                return 0;
            }
        }
  
        // x is prime
        return 1;
    }
  
    // 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 n = Integer.parseInt(args[0]);
  
            // Check if n is prime
            if (isPrime(n) == 1)
                System.out.println("Yes");
            else
                System.out.println("No");
        }
        else
            System.out.println("No command line "
                               + "arguments found.");
    }
}

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Output:

  • In C:

  • In Java:



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