【easy】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]

/*可以先找到最大的回文数，再检查能否被分解，如果不能就再找仅次于这个回文数的小回文数：*/

class Solution {

public:

    int largestPalindrome(int n) {

        if(n==) return ;

        int upper = pow(, n) - ;

        int lower = pow(, n - );

        for (int i = upper; i > lower; --i) {

            long long cand = creatPalindrome(i);

            for (int j = upper; cand / j < j; --j) {

                if (cand % j == ) return cand % ;

            }

        }

        return -;

    }

private:

    long long creatPalindrome(int n) {

        string lastHalf = to_string(n);

        reverse(lastHalf.begin(), lastHalf.end());

        return stoll(to_string(n) + lastHalf);

    }

};