Add kaprekarNumberInRange (TheAlgorithms#2894)

Co-authored-by: Andrii Siriak <[email protected]>

Author: subhroacharjee

src/main/java/com/thealgorithms/maths/KaprekarNumbers.java

@@ -1,20 +1,33 @@
 package com.thealgorithms.maths;
+import java.util.*;
 
 public class KaprekarNumbers {
 
 	/* This program demonstrates if a given number is Kaprekar Number or not.
 	Kaprekar Number: A Kaprekar number is an n-digit number which its square can be split into two parts where the right part has n
 	digits and sum of these parts is equal to the original number. */
 
-	// Checks whether a given number is Kaprekar Number or not
+	// Provides a list of kaprekarNumber in a range
+	public static ArrayList<Long> kaprekarNumberInRange(long start, long end) throws Exception {
+		long n = end-start;
+		if (n <0) throw new Exception("Invalid range");
+		ArrayList<Long> list = new ArrayList<>();
+
+		for (long i = start; i <= end; i++) {
+			if (isKaprekarNumber(i)) list.add(i);
+		}
 
-	public static boolean isKaprekarNumber(long number) {			
+		return list;
+	}
+
+	// Checks whether a given number is Kaprekar Number or not
+	public static boolean isKaprekarNumber(long number) {
 		long numberSquared = number * number;
 		if(Long.toString(number).length() == Long.toString(numberSquared).length()){
 			return (number == numberSquared);
 		}
 		else{
-			long leftDigits1 = 0, leftDigits2 = 0;
+			long leftDigits1 = 0, leftDigits2;
 			if(Long.toString(numberSquared).contains("0")){
 				leftDigits1 = Long.parseLong(Long.toString(numberSquared).substring(0, Long.toString(numberSquared).indexOf("0")));
 			}