Submission #3215578

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll N=20,M=1<<20;
const ll ms=1e9+7;
ll read(){
	ll x=0,f=1; char ch=getchar();
	while (ch<'0'||ch>'9'){if (ch=='-') f=-1; ch=getchar();}
	while (ch>='0'&&ch<='9'){x=x*10+ch-'0'; ch=getchar();}
	return x*f;
}
ll a[M],inv[M],fac[M],f[2][M];
void pre(ll n){
	inv[0]=inv[1]=fac[0]=fac[1]=1;
	for (ll i=2;i<=n;i++){
		inv[i]=(ms-ms/i)*inv[ms%i]%ms;
		fac[i]=fac[i-1]*i%ms;
	}
	for (ll i=2;i<=n;i++)
	inv[i]=inv[i-1]*inv[i]%ms;
}
ll C(ll n,ll k){
	return (fac[n]*inv[n-k]%ms*inv[k]%ms)%ms;
}
bool cmp(ll a,ll b){
	return a>b;
}
int main(){
	ll n=read(),m=read();
	for (ll i=1;i<=m;i++)
    scanf("%lld",&a[i]);
    sort(a+1,a+1+m,cmp);
    pre(1<<n);
    ll now=0;
    f[now][0]=1;
    for (ll i=1;i<=m;i++){
    	now^=1;
    for (ll j=0;j<(1<<n);j++){
    	if (f[now^1][j]==0) continue;
    	f[now][j]=(f[now][j]+f[now^1][j])%ms;
    	ll res=(1<<n)-j-1;
    	for (ll k=0;k<(n);k++){
    		if ((j&(1<<k))==0){
    			f[now][j|(1<<k)]+=((f[now^1][j]*C(res-a[i]+1,(1<<k)-1)%ms*fac[1<<k])%ms);
    			f[now][j|(1<<k)]%=ms;
			}
		}
	   }	
	   memset(f[now^1],0,sizeof(f[now^1]));
	}
	ll ans=0;
	for (ll i=0;i<(1<<n);i++){
		if (f[now][i]==0) continue;
		ll fs=1;
		if ((__builtin_popcount(i)%2)==1) fs*=-1;
		ans=(ans+fs*f[now][i]*fac[(1<<n)-1-i]%ms)%ms;
	}
	if (ans<0) ans+=ms;
	(ans<<=n)%=ms;
	printf("%lld\n",ans);
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:31:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld",&a[i]);
                        ^

Judge Result