Question

I have this problem:

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.
Input

The first line contains integer t, the number of test cases. Integers K are given in the next t lines.
Output

For each K, output the smallest palindrome larger than K.
Example

Input:

2
808
2133

Output:

818
2222

My code converts the input to a string and evaluates either end of the string making adjustments accordingly and moves inwards. However, the problem requires that it can take values up to 10^6 digits long, if I try to parse large numbers I get a number format exception i.e.

Integer.parseInt(LARGENUMBER);

or

Long.parseInt(LARGENUMBER);

and LARGENUMBER is out of range. can anyone think of a work around or how to handle such large numbers?

Answer 1

You could probably use the BigInteger class to handle large integers like this.

However, I wouldn’t count on it being efficient at such massive sizes. Because it still uses O(n^2) algorithms for multiplication and conversions.