n 小于等于 10^6
by Mq_Gu1231 @ 2024-03-24 13:21:30
@[Mq_Gu1231](/user/764620) dp[i][0/1/2]
by XuYueming @ 2024-03-24 13:26:03
?没看懂，ai没有值域限制吗
by long_ting @ 2024-03-24 13:34:18
可能没有很全面理解题目的意思，仅供参考，用的c++。
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```cpp
#include <iostream>
using namespace std;
const int MOD = 1e9 + 7;
// 快速幂模运算，计算 x^n % MOD
long long powmod(long long x, long long n, long long mod) {
long long result = 1;
x = x % mod;
while (n > 0) {
if (n & 1) result = (result * x) % mod;
x = (x * x) % mod;
n >>= 1;
}
return result;
}
int main() {
long long n;
cin >> n;
// 计算答案
long long total = powmod(10, n, MOD);
long long noZero = powmod(9, n, MOD);
long long noNine = noZero; // 和没有 0 的情况一样
long long noZeroNoNine = powmod(8, n, MOD);
long long answer = (total - 2 * noZero + noZeroNoNine) % MOD;
// 由于 MOD 是质数，使用加 MOD 确保结果为正
if (answer < 0) answer += MOD;
cout << answer << endl;
return 0;
}
```
by XiaoJiang0112 @ 2024-03-24 13:48:09
@[Mq_Gu1231](/user/764620) 忘记at你了
by XiaoJiang0112 @ 2024-03-24 13:49:17
忘写了，ai小于等于9（补充）
by Mq_Gu1231 @ 2024-03-24 14:51:59
@[XiaoJiang0112](/user/1302707) 谢谢
by Mq_Gu1231 @ 2024-03-24 14:52:19