Karpreakr.java

import java.util.Scanner;

// Java program to check if a number is
// Kaprekar number or not

class Karepreakr
{
	// Returns true if n is a Kaprekar number, else false
	static boolean iskaprekar(int n)
	{
		if (n == 1)
		return true;
	
		// Count number of digits in square
		int sq_n = n * n;
		int count_digits = 0;
		while (sq_n != 0)
		{
			count_digits++;
			sq_n /= 10;
		}
	
		sq_n = n*n; // Recompute square as it was changed
	
		// Split the square at different points and see if sum
		// of any pair of splitted numbers is equal to n.
		for (int r_digits=1; r_digits<count_digits; r_digits++)
		{
			int eq_parts = (int) Math.pow(10, r_digits);
	
			// To avoid numbers like 10, 100, 1000 (These are not
			// Kaprekar numbers
			if (eq_parts == n)
				continue;
	
			// Find sum of current parts and compare with n
			int sum = sq_n/eq_parts + sq_n % eq_parts;
			if (sum == n)
			return true;
		}
	
		// compare with original number
		return false;
	}
	
	// Driver method
	public static void main (String[] args)
	{
		System.out.println("Printing first few Kaprekar Numbers" +
							" using iskaprekar()");
                            
           System.out.println("Enter the number you want to check!");                 
          Scanner sc=new Scanner(System.in);                  
          int n=sc.nextInt();                  
		
		for (int i=1; i<n; i++)
			if (iskaprekar(i))
				System.out.print(i + " ");
	}
}