Submission #1628505

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Source Code Expand

#include"bits/stdc++.h"


#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x,"r",stdin)
#define fw(x) freopen(x,"w",stdout)
#define iout(x) printf("%d\n",x)
#define lout(x) printf("%lld\n",x)
#define REP(x,l,u) for(int x = (l);x<=(u);x++)
#define RREP(x,l,u) for(int x = (l);x>=(u);x--)
#define mst(x,a) memset(x,a,sizeof(x))
#define PII pair<int,int>
#define PLL pair<ll,ll>
#define MP make_pair
#define se second
#define fi first
#define dbg(x) cout<<#x<<" = "<<(x)<<endl;
#define sz(x) ((int)x.size())
#define cl(x) x.clear()

typedef  long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace std;

const int maxn = 100010;
const int mod = 1e9+7;
const double eps = 1e-6;
const double PI = acos(-1);

template<typename T> inline void read(T &x){
x=0;T f=1;char ch;do{ch=getchar();if(ch=='-')f=-1;}while(ch<'0'||ch>'9');do x=x*10+ch-'0',ch=getchar();while(ch<='9'&&ch>='0');x*=f;
}

template<typename A,typename B> inline void read(A&x,B&y){read(x);read(y);}
template<typename A,typename B,typename C> inline void read(A&x,B&y,C&z){read(x);read(y);read(z);}
template<typename A,typename B,typename C,typename D> inline void read(A&x,B&y,C&z,D&w){read(x);read(y);read(z);read(w);}
template<typename A,typename B> inline A fexp(A x,B p){A ans=1;for(;p;p>>=1,x=1LL*x*x%mod)if(p&1)ans=1LL*ans*x%mod;return ans;}
template<typename A,typename B> inline A fexp(A x,B p,A mo){A ans=1;for(;p;p>>=1,x=1LL*x*x%mo)if(p&1)ans=1LL*ans*x%mo;return ans;}

int n,m;

int has[1<<16],nm[1<<16];

int f[1<<16];

void Work(){
	for(int sta=0;sta<1<<n;sta++)nm[sta]=nm[sta>>1]+(sta&1);
	f[0]=1;
	for(int sta=0;sta<1<<n;sta++)if((sta&3)==3||(sta&3)==0){
		for(int s=sta;s;s=(s-1)&sta){
			int ans=1;
			REP(i,1,n)if(((sta^s)>>i-1)&1)ans=1LL*ans*(fexp(2,nm[has[i]&s])-1)%mod;
			int tmp=0;
			REP(i,1,n)if((s>>i-1)&1)tmp+=nm[has[i]&(sta^s)];
//			if(ans&&f[sta^s])cout<<sta<<' '<<s<<' '<<1LL*f[sta^s]*ans%mod*fexp(2,tmp)<<' '<<tmp<<endl;
			f[sta]=(f[sta]+1LL*f[sta^s]*ans%mod*fexp(2,tmp))%mod;
		}
//		cout<<sta<<' '<<f[sta]<<endl;
	}
	iout((fexp(2,m)-f[(1<<n)-1]+mod)%mod);
}

void Init(){
	read(n,m);
	REP(i,1,m){
		int u,v;
		read(u,v);
		has[u]|=1<<v-1;
	}
}

int main(){
	Init();
	Work();
	return 0;
}

Submission Info

Judge Result