leetcode 479. Largest Palindrome Product 最大的回文数字 + 直接暴力真好

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].

想了好久才明白直接遍历所有的可能即可

建议和leetcode 680. Valid Palindrome II 去除一个字符的回文字符串判断 + 双指针 一起学习

代码如下：

#include <iostream>
#include <vector>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <queue>
#include <stack>
#include <string>
#include <climits>
#include <algorithm>
#include <sstream>
#include <functional>
#include <bitset>
#include <numeric>
#include <cmath>
#include <regex>
#include <iomanip>
#include <cstdlib>
#include <ctime>

using namespace std;

class Solution
{
public:
int largestPalindrome(int n)
{
if (n == 1)
return 9;

int maxNum = pow(10, n), minNum = pow(10, n - 1);
for (int i = maxNum; i >= minNum; i--)
{
string a = to_string(i), b = a;
reverse(b.begin(), b.end());
long long now = stoll(a + b);
for (int j = maxNum; j >= minNum; j--)
{
if (now / j >= maxNum)
break;
else if (now%j == 0)
return now % 1337;
}
}
return -1;
}
};