A positive integer is called a palindrome if its representation in the decimal system is the same when read from left to right and from right to left. For a given positive integer K of not more than 1000000 digits, write the value of the smallest palindrome larger than K to output. Numbers are always displayed without leading zeros.
import java.util.Scanner;
class next{
public static void main(String ags[])
{
Scanner in = new Scanner(System.in);
int n=in.nextInt();
for(int i=0;i<n;i++)
{
String s = in.next();
if(s.length()%2==0)
{
int p = s.length()/2;
String sub = s.substring(0,p);
String sub2= s.substring(p,s.length());
String reverse = new StringBuffer(sub).reverse().toString();
int t = Integer.parseInt(reverse);
int t1= Integer.parseInt(sub2);
if(t>t1)
{
System.out.println(sub+reverse);
}
else
{
int t2 = Integer.parseInt(sub)+1;
String s2 = Integer.toString(t2);
String rev = new StringBuffer(s2).reverse().toString();
System.out.println(s2+rev);
}
}
else
{
int len = s.length()/2;
String se1 = s.substring(0,len);
String se2 = s.substring(len+1,s.length());
String reverse = new StringBuffer(se1).reverse().toString();
int t = Integer.parseInt(reverse);
int t1= Integer.parseInt(se2);
if(t>t1)
{
String se = s.substring(0,len+1);
System.out.println(se+reverse);
}
else
{
String temp = s.substring(0,len+1);
int tn = Integer.parseInt(temp);
tn++;
String left = Integer.toString(tn);
String grip = left.substring(0,left.length()-1);
String reve = new StringBuffer(grip).reverse().toString();
System.out.println(left+reve);
}
}
}
}
}
I am a beginner to programming.I am trying to solve this question #PALIN on spoj , but I am getting runtime error even though it is working on ideone.please help me
There are a few problems with your code, but the biggest is that you're calling Integer.parseInt on strings that can represent values far outside the range of int. The instructions say that the input can be up to a million digits, which means that you're calling Integer.parseInt on strings of up to half a million digits — meaning, strings of up to 10500000−1 — but ints only go up to 231−1, which is less than 1010.
Once you've fixed that, you can test your code by doing the following:
String computeNextPalindrome(String s). That way, you can test that method by programmatically calling it and examining its result, rather than messing around with standard output.expectedResult to the expected result of computeNextPalindrome("99999") (namely "100001") and then iterates downward from 99999 to 1, verifying that computeNextPalindrome always returns expectedResult. After each verification, check if the current number is a palindrome, and if so, update expectedResult to the current number.That way, you can exhaustively test that your logic is correct for all numbers up to five digits. Aside from the bug I mentioned above, about trying to use int for values well outside the range of int, most bugs will show up for some small cases. It's rather unusual to have a bug that only affects large values; so by exhaustively testing small values, you can find almost all bugs.
You can then check for bugs specific to large values by spot-testing a few large values, like "1234567890123456789012345678901234568790" (which should give "1234567890123456789119876543210987654321").