提出 #28671151

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ソースコード 拡げる

#include<bits/stdc++.h>
#define L(i, j, k) for(int i = (j); i <= (k); ++i)
#define R(i, j, k) for(int i = (j); i >= (k); --i)
#define ll long long
#define vi vector <int>
#define sz(a) ((int) (a).size())
#define me(f, x) memset(f, x, sizeof(f))
using namespace std;
const int N = 55, mod = 1e9 + 7;
int n, dp[N][N][N], ns; // used; cur1; cur2; 
int qpow(int x, int y = mod - 2) {
	int res = 1;
	for(; y; x = (ll) x * x % mod, y >>= 1) if(y & 1) res = (ll) res * x % mod;
	return res;
}
int fac[N], ifac[N], inv[N];
void init(int x) {
	fac[0] = ifac[0] = inv[1] = 1;
	L(i, 2, x) inv[i] = (ll) (mod - mod / i) * inv[mod % i] % mod;
	L(i, 1, x) fac[i] = (ll) fac[i - 1] * i % mod, ifac[i] = (ll) ifac[i - 1] * inv[i] % mod;
} 
int C(int x, int y) {
	return x < y || y < 0 ? 0 : (ll) fac[x] * ifac[y] % mod * ifac[x - y] % mod;
}
int main () {
	ios :: sync_with_stdio(false);
	cin.tie (0); cout.tie (0);
	cin >> n;
	init (n);
	dp[0][0][0] = 1;
	L(i, 0, n) {
		L(x, 0, n) {
			L(y, 0, n) if(dp[i][x][y]) {
				int up = n - i, dt = abs (x - y);
				if (x >= y) {
					L(u, 0, up) L(v, dt, up) if(u + v && u + v <= up) 
						(dp[i + u + v][u + dt][v - dt] += 
							(ll) dp[i][x][y] * ifac[u] % mod * ifac[v] % mod) %= mod;
				} else {
					L(u, dt, up) L(v, 0, up) if(u + v && u + v <= up) 
						(dp[i + u + v][u - dt][v + dt] += 
							(ll) dp[i][x][y] * ifac[u] % mod * ifac[v] % mod) %= mod;
				}
			}
		}
	}
	cout << (ll) dp[n][1][0] * fac[n] % mod << '\n';
	return 0;
}

提出情報

ジャッジ結果