479. Largest Palindrome Product

Find the largest palindrome made from the product of two n-digit numbers.

Since the result could be very large, you should return the largest palindrome mod 1337.

Example:

Input: 2

Output: 987

Explanation: 99 x 91 = 9009, 9009 % 1337 = 987

Note:

The range of n is [1,8].

思路：
分析：当n=1时，结果为9.
当n>1时，两个n位数相乘最大回文结果必然是2n位数的。
可以先构造回文，然后判断是否能够分解成2个n位数相乘。

class Solution {
    public int largestPalindrome(int n) {
        if(n == 1)
            return 9;
        int maxNumber=(int)Math.pow(10,n)-1;
        for(int i = maxNumber;i > maxNumber / 10;i--){
            long num = palindrome(i);
            for(long j = maxNumber;j * j >= num;j--){
                if(num % j==0)
                    return (int)(num % 1337);
            }
        }
        return 0;
    }
    public long palindrome(int i){
        StringBuffer s = new StringBuffer();
        s.append(Integer.toString(i)).reverse();
        return