Submission #19735

#	Time	Username	Problem	Language	Result	Execution time	Memory
19735		algoshipda	괄호 (kriii4_R)	C++14	0 / 100	65 ms	5628 KiB

R

#include <bits/stdc++.h>
using namespace std;

typedef long long lld;
const int MOD = 1e9 + 7;
const int MN = 1e6 + 10;
int fpow(int n, int k)
{
	if(k == 0) return 1;
	if(k % 2){
		return 1ll * n * fpow(n, k - 1) % MOD;
	}
	int h = fpow(n, k / 2);
	return 1ll * h * h % MOD;
}

inline int inv(int n)
{
	return 1ll * fpow(n, MOD - 2) % MOD;
}

inline void mult(int& a, int b)
{
	a = 1ll * a * b % MOD;
}

inline int mult2(int a, int b)
{
	return 1ll * a * b % MOD;
}

inline void sub(int& a, int b)
{
	a = ((a - b) % MOD + MOD) % MOD;
}

inline int rational(int a, int b)
{
	return 1ll * a * inv(b) % MOD;
}

inline void add(int &a, int b)
{
	a = ((a + b) % MOD + MOD) % MOD;
}


int pmul[MN];
inline int nPr(int n, int r)
{
	return mult2(pmul[n], inv(pmul[n - r]));
}

int main()
{
	int n, k;
	cin >> n >> k;
	pmul[0] = 1;
	for(int i = 1; i <= n; ++i){
		pmul[i] = mult2(i, pmul[i - 1]);
	}
	int ans = 0;
	for(int i = n / 2 + n % 2; i <= n; ++i){
		add(ans, nPr(i, n - i));
	}
	cout << ans << '\n';
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 92