Submission #1405173

---

Source Code Expand

#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep1(i,n) for(int i=1;i<=(int)(n);i++)
#define all(c) c.begin(),c.end()
#define pb push_back
#define fs first
#define sc second
#define show(x) cout << #x << " = " << (x) << endl
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
using namespace std;
template<class S,class T> ostream& operator<<(ostream& o,const pair<S,T> &p){return o<<"("<<p.fs<<","<<p.sc<<")";}
template<class T> ostream& operator<<(ostream& o,const vector<T> &vc){o<<"sz = "<<vc.size()<<endl<<"[";for(const T& v:vc) o<<v<<",";o<<"]";return o;}
template<unsigned int mod_>
struct ModInt{
	using uint = unsigned int;
	using ll = long long;
	using ull = unsigned long long;

	constexpr static uint mod = mod_;

	uint v;
	ModInt():v(0){}
	ModInt(ll v):v(normS(v%mod+mod)){}
	explicit operator bool() const {return v!=0;}
	static uint normS(const uint &x){return (x<mod)?x:x-mod;}		// [0 , 2*mod-1] -> [0 , mod-1]
	static ModInt make(const uint &x){ModInt m; m.v=x; return m;}
	ModInt operator+(const ModInt& b) const { return make(normS(v+b.v));}
	ModInt operator-(const ModInt& b) const { return make(normS(v+mod-b.v));}
	ModInt operator-() const { return make(normS(mod-v)); }
	ModInt operator*(const ModInt& b) const { return make((ull)v*b.v%mod);}
	ModInt operator/(const ModInt& b) const { return *this*b.inv();}
	ModInt& operator+=(const ModInt& b){ return *this=*this+b;}
	ModInt& operator-=(const ModInt& b){ return *this=*this-b;}
	ModInt& operator*=(const ModInt& b){ return *this=*this*b;}
	ModInt& operator/=(const ModInt& b){ return *this=*this/b;}
	ll extgcd(ll a,ll b,ll &x,ll &y) const{
		ll u[]={a,1,0},v[]={b,0,1};
		while(*v){
			ll t=*u/ *v;
			rep(i,3) swap(u[i]-=t*v[i],v[i]);
		}
		if(u[0]<0) rep(i,3) u[i]=-u[i];
		x=u[1],y=u[2];
		return u[0];
	}
	ModInt inv() const{
		ll x,y;
		extgcd(v,mod,x,y);
		return make(normS(x+mod));
	}
	bool operator==(const ModInt& b) const { return v==b.v;}
	bool operator!=(const ModInt& b) const { return v!=b.v;}
	friend istream& operator>>(istream &o,ModInt& x){
		ll tmp;
		o>>tmp;
		x=ModInt(tmp);
		return o;
	}
	friend ostream& operator<<(ostream &o,const ModInt& x){ return o<<x.v;}
};
using mint = ModInt<1000000007>;
bool B(int x,int i){return (x>>i)&1;}

int N,M;
bool e[15][15];
int edgenum[15][1<<15];
mint dp[1<<15][2];

int calcedgenum(int x,int S){	//from x to S
	int n = 0;
	rep(i,N) if(B(S,i) && e[x][i]) n++;
	return n;
}
void precalc(){
	rep(x,N) rep(b,1<<N) edgenum[x][b] = calcedgenum(x,b);
}

mint p2[1000];

int main(){
	p2[0] = 1;
	rep1(i,999) p2[i] = p2[i-1]*2;
	cin>>N>>M;
	rep(i,M){
		int x,y;
		cin>>x>>y;
		x--,y--;
		e[x][y] = 1;
	}
	precalc();
	dp[0][0] = 1;
	rep(b,1<<N) rep(t,2) if(dp[b][t]){
		int nb = (1<<N)-1 - b;
		for(int c = nb;c!=0;c=(c-1)&nb){
			int d = nb-c;
			mint coef = 1;
			rep(x,N) if(B(d,x)){
				int n = edgenum[x][c];
				coef *= (p2[n]-1);
			}
			rep(x,N) if(B(b,x)){
				int n = edgenum[x][c];
				coef *= p2[n];
			}
			int nt = t || (B(c,0)&&B(c,1));
			dp[b|c][nt] += dp[b][t] * coef;
		}
	}
	cout<<dp[(1<<N)-1][0]<<endl;
}

Submission Info

Judge Result