Palindromic Squares - USACO 1.2.4

palindromicsquares - codetrick
Palindromes are numbers that read the same forwards as backwards. The number 12321 is a typical palindrome.
Given a number base B (2 <= B <= 20 base 10), print all the integers N (1 <= N <= 300 base 10) such that the square of N is palindromic when expressed in base B; also print the value of that palindromic square. Use the letters 'A', 'B', and so on to represent the digits 10, 11, and so on.
Print both the number and its square in base B.

PROGRAM NAME: palsquare

INPUT FORMAT

A single line with B, the base (specified in base 10).

SAMPLE INPUT (file palsquare.in)

10  

OUTPUT FORMAT

Lines with two integers represented in base B. The first integer is the number whose square is palindromic; the second integer is the square itself.

SAMPLE OUTPUT (file palsquare.out)

1 1  2 4  3 9  11 121  22 484  26 676  101 10201  111 12321  121 14641  202 40804  212 44944  264 69696

http://code.antonio081014.com/2012/09/usaco-palindromic-squares.html

    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(new File("palsquare.in"));
        PrintWriter pw = new PrintWriter(new File("palsquare.out"));

        int base = sc.nextInt();

        for (int i = 1; i <= 300; i++) {
            String square = Integer.toString(i * i, base).toUpperCase();
            // String square = toBase(i * i, base, rep);
            if (isPalindrome(square)) {
                pw.println(Integer.toString(i, base).toUpperCase() + " "
                        + square);
            }
        }

        pw.close();
    }

    private static boolean isPalindrome(String input) {
        for (int i = 0; i < input.length() / 2; i++) {
            if (input.charAt(i) != input.charAt(input.length() - i - 1))
                return false;
        }
        return true;
    }

    private static String toBase(int i, int base, char[] rep) {
        StringBuilder sb = new StringBuilder();
        int val = i;
        while (val >= base) {
            sb.insert(0, rep[val % base]);
            val = val / base;
        }
        return sb.insert(0, rep[val]).toString();
    }

http://acm.sdibt.edu.cn/blog/?p=1461
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