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QOJ

IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#409018#6734. Click the CircleGepiSAMA#WA 1ms4272kbC++142.0kb2024-05-11 15:43:342024-05-11 15:43:34

Judging History

你现在查看的是最新测评结果

  • [2024-05-11 15:43:34]
  • 评测
  • 测评结果:WA
  • 用时:1ms
  • 内存:4272kb
  • [2024-05-11 15:43:34]
  • 提交

answer



#include <iostream>
#include <cstring>

using namespace std;

using i64 = long long;

const int mod = 1e9 + 7;
const int N = 210;

int fac[N], invfac[N];
int f[N], g[N];
int n, k;
i64 t;

int qpow(int a, int b) {
	int res = 1;
	while (b) {
		if (b & 1) res = 1ll * res * a % mod;
		a = 1ll * a * a % mod;
		b >>= 1;
	}	
	return res;
}

int inv(int x) {
	return qpow(x, mod - 2);
}

void init_fac(int n) {
	fac[0] = 1;
	for (int i = 1; i <= n; i++) {
		fac[i] = 1ll * fac[i - 1] * i % mod;
	}
	invfac[n] = inv(fac[n]);
	for (int i = n - 1; ~i; i--) {
		invfac[i] = 1ll * invfac[i + 1] * (i + 1) % mod;
	}
}

int binom(int a, int b) {
	if (a < b) return 0;
	return 1ll * fac[a] * invfac[b] % mod * invfac[a - b] % mod;
}

struct Matrix {
	int v[N][N];	
	Matrix (int t = 0) {
		memset(v, 0, sizeof v);
		for (int i = 0; i <= n; i++) {
			v[i][i] = t;
		} 
	}
	
	Matrix operator* (Matrix& b) {
		Matrix c;
		for (int i = 0; i <= n; i++)
                        for (int j = 0; j <= n; j++)
                                for (int k = 0; k <= n; k++)
                                        c.v[i][j] = (c.v[i][j] + 1ll * v[i][k] * b.v[k][j] % mod) % mod;
		return c;
	}
	
	Matrix operator^ (i64 b) {
		Matrix res = 1, a = *this;
		while (b) {
			if (b & 1) res = res * a;
			a = a * a;
			b >>= 1;
		}
		return res;
	}
};

int main() {
	cin >> n >> t >> k;
	Matrix B;
	B.v[0][0] = B.v[n][n] = 1;
	for (int i = 1; i < n; i++) {
		B.v[i][i] = 1ll * (i * i + (n - i) * (n - i)) * inv(n * n) % mod;
		B.v[i][i - 1] = B.v[i][i + 1] = 1ll * (n * i - i * i) * inv(n * n) % mod;
	}
	B = B ^ t;	
	for (int i = 0; i <= n; i++) {
		g[i] = B.v[i][0];
	}
	init_fac(n);
	for (int i = n; ~i; i--) {
	        f[i] = g[i];
		for (int j = i + 1; j <= n; j++) {
			f[i] -= 1ll * binom(n - i, j - i) * f[j] % mod;
			f[i] = (f[i] + mod) % mod;
		}	    
	}
	int res = 0;
	for (int i = 0; i <= n - k; i++) {
		res += 1ll * binom(n, i) * f[i] % mod;
		res %= mod;
	}
	cout << res << '\n';
	return 0;    
}

Details

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Test #1:

score: 100
Accepted
time: 1ms
memory: 4244kb

input:

2 1 1
1 1 1 2
1 2 2 3

output:

1

result:

ok 1 number(s): "1"

Test #2:

score: -100
Wrong Answer
time: 1ms
memory: 4272kb

input:

2 1 1
1 1 1 2
1 3 2 3

output:

1

result:

wrong answer 1st numbers differ - expected: '0', found: '1'