Submission #1886980

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Source Code Expand

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

typedef pair<int, int> pii;
typedef long long ll;
typedef vector<int> vi;

#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fi first
#define se second
#define rep(i,n) rep2(i,0,n)
#define rep2(i,m,n) for(int i=m;i<(n);i++)
#define ALL(c) (c).begin(),(c).end()

const ll MOD = 1000000007;

int N, M;
ll p2[310];
bool e[16][16];
ll dp[1 << 15];

int main() {
	p2[0] = 1;
	for (int i = 1; i < 310; ++i) {
		p2[i] = p2[i-1] * 2 % MOD;
	}

	cin >> N >> M;

	rep(i, M) {
		int x, y;
		cin >> x >> y;
		--x; --y;
		e[x][y] = 1;
	}

	dp[0] = 1;

	for (int i = 1; i < (1 << N); ++i) {
		for (int j = i; j >= 0; --j) {
			j &= i;

			int nx = j ^ i;
			if (dp[j] == 0 || ((nx & 1) && (nx & 2))) {
				continue;
			}

			int rem = ((1 << N) - 1) ^ i;

			ll way = 1;

			rep(k, N) {
				if ((rem >> k) & 1) {
					int cnt = 0;
					rep(t, N) if ((nx >> t) & 1) {
						if (e[k][t]) {
							++cnt;
						}
					}
					way = way * (p2[cnt] - 1) % MOD;
				} else if ((j >> k) & 1) {
					int cnt = 0;
					rep(t, N) if ((nx >> t) & 1) {
						if (e[k][t]) {
							++cnt;
						}
					}
					way = way * p2[cnt] % MOD;	
				}
			}

			dp[i] = (dp[i] + dp[j] * way) % MOD;
		}
	}


	cout << dp[(1 << N) - 1] << endl;

    return 0;
}

Submission Info

Judge Result