479. Largest Palindrome Product

[namespace-io]

class Solution {
public:
    int largestPalindrome(int n) {
        if(n == 1) return 9;
        int upper = pow(10, n) - 1;
        int lower = pow(10, n-1);
        for(int d = upper; d >= lower; d--){
            long p = buildPa(d);
            for(long m = upper; m * m >= p; m--){
                if(p % m == 0) return p % 1337;
            }
        }
        
        return 0;
    }
    
    long buildPa(int d){
        string s = to_string(d);
        reverse(s.begin(), s.end());
        return stol(to_string(d) + s);
    }
};