Java program to check for Fascinating Number

Write a Program in Java to input a number and check whether it is a Fascinating Number or not..

Fascinating Numbers : Some numbers of 3 digits or more exhibit a very interesting property. The property is such that, when the number is multiplied by 2 and 3, and both these products are concatenated with the original number, all digits from 1 to 9 are present exactly once, regardless of the number of zeroes.

Let’s understand the concept of Fascinating Number through the following example:

Consider the number 192,
192 x 1 = 192
192 x 2 = 384
192 x 3 = 576

Concatenating the results : 192384576

It could be observed that ‘192384576’ consists of all digits from 1 to 9 exactly once. Hence, it could be concluded that 192 is a Fascinating Number.

Some examples of fascinating Numbers are : 192, 219, 273, 327, 1902, 1920, 2019 etc.

import java.util.*;

class FascinatingNumber

{

    boolean isUnique(String q)

    {

        int A[] = {0,0,0,0,0,0,0,0,0,0}; //to store frequency of every digit from '0' to '9'

        int i, flag = 0;

        char ch;

        for(i=0; i<q.length(); i++)

        {

            ch = q.charAt(i);

            A[ch-48]++;

            /*  increasing A[5] if ch='5' as '5'-48 = 53-48=5

             *  (ASCII values of '0' to '9' are 48 to 57) */

        }

 

        for(i=1; i<10; i++)

        {

            //checking if every digit from '1' to '9' are present exactly once or not

            if(A[i]!=1)

            {

                flag = 1; //flag is set to 1 if frequency is not 1

                break;

            }

        }

 

        if(flag == 1)

            return false;

        else

            return true;

    }

    public static void main(String args[])

    {

        Scanner sc = new Scanner(System.in);

        FascinatingNumber ob = new FascinatingNumber();

 

        System.out.print("Enter a number : ");

        int n = sc.nextInt();

        String p = Integer.toString(n); //converting the number to String

 

        if(p.length()<3)

            System.out.println("Number should be of atleast 3 digits.");

 

        else

        {

            String s = Integer.toString(n*1) + Integer.toString(n*2) + Integer.toString(n*3);

            /*  Joining the first, second and third multiple of the number

             *  by converting them to Strings and concatenating them*/

            if(ob.isUnique(s))

                System.out.println(n+" is a Fascinating Number.");

            else

                System.out.println(n+" is not a Fascinating Number.");

        }      

    }

}







Output:

Enter a number : 273 273 is a Fascinating Number.   Enter a number : 853 853 is not a Fascinating Number.   Enter a number : 95 Number should be of atleast 3 digits.