牛客寒假算法基础集训营5 J 炫酷数学

题解

对于每个二进制位有三对(0, 0), (0, 1), (1, 0)则n位二进制位有3^n个 对998244353取模即可

AC代码

#include 
#include 
using namespace std;
typedef long long ll;

const int INF = 0x3f3f3f3f;
const int MOD = 998244353;

ll mpow(ll a, ll n, ll m) //a ^ n % m
{
	ll t = 1;
	while (n)
	{
		if (n & 1)
			t = (t * a) % m;
		a = (a * a) % m, n >>= 1;
	}
	return t;
}
int main()
{
#ifdef LOCAL
	//freopen("C:/input.txt", "r", stdin);
#endif	
	int n;
	cin >> n;
	cout << mpow(3, n, MOD) << endl;

	return 0;
}