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Reverse and Add Function in Java
We are given with an integer and the agenda here is to reverse the digits of the number and add the reversed number to the original number and check if the resultant number is a palindrome or not and the process is repeated until it does. The breaking point of the process is 1000 iterations and a value greater than the maximum long value( Long.MAX_VALUE).
For Examples
Input − 1678
Output − Palindrome of the given input 1678 293392
Explanation − The input number is first reversed and then added to the original number, it is then checked for palindrome if it is not a palindrome then the same process is repeated on the updated number. The breaking point of the process is 1000 iterations and a value greater than the maximum long value( Long.MAX_VALUE).
Input − 202021038
Output − Palindrome of the given input 202021038 1453553541
Explanation − The input number is first reversed and then added to the original number, it is then checked for palindrome if it is not a palindrome then the same process is repeated on the updated number. The breaking point of the process is 1000 iterations and a value greater than the maximum long value( Long.MAX_VALUE).
Approach used in the below program is as follows
Inside the main function
The input number is passed in the method calculateReverseandAdd(input)
Inside the method calculateReverseandAdd
A new variable rev_number is introduced
A loop is iterated with the condition number <= max
Inside the loop, the reverse of the number is obtained by passing the number through the method reverseNumber()
The reversed number is then added to the input number
The obtained number is then checked for palindrome by passing the number in the method checkPalindrome(), If yes the number is printed as output to the user.
If the number is not palindrome then the same process is repeated with the obtained number till a palindrome is obtained, if the resultant number is greater than the maximum long value then no possible palindrome is in the range for the given number exist.
Example
import java.util.*;
public class ReverseAdd{
static final long max = Long.MAX_VALUE;
static long reverseNumber(long number){
long rev_number = 0;
while (number > 0){
rev_number = rev_number * 10 + number % 10;
number = number / 10;
}
return rev_number;
}
static boolean checkPalindrome(long number){
return (reverseNumber(number) == number);
}
static void calculateReverseandAdd(long number){
long rev_number = 0;
System.out.println("Palindrome of the given input " + number);
while (number <= max){
rev_number = reverseNumber(number);
number = number + rev_number;
if (checkPalindrome(number)){
System.out.println(number);
break;
}
else if (number > max){
System.out.println("No possible palindromes for the input");
}
}
}
public static void main(String[] args){
calculateReverseandAdd(1678);
calculateReverseandAdd(2961);
calculateReverseandAdd(202021038);
}
}Output
If we run the above code it will generate the following Output
Palindrome of the given input 1678 293392 Palindrome of the given input 2961 69696 Palindrome of the given input 202021038 1453553541
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