Largest Palindrome Product问题及解法

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

示例：

Input: 2

Output: 987

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

Note:

The range of n is [1,8].

问题分析：

求出n为整数的最大值，从最大依次到最小构造回文数，对于构造出的回文数，进行判断是否是两个n位数相乘的积。

过程详见代码：

class Solution {
public:int largestPalindrome(int n) {if (n == 1) return 9;int max = pow(10, n) - 1;for (int v = max - 1; v > max / 10; v--){string s = to_string(v);reverse(s.begin(), s.end());s = to_string(v) + s;long long u = stol(s);for (long long x = max; x*x >= u; x--)if (u%x == 0)return (int)(u % 1337);}return 0;}
};