Submission #1083613

#	Time	Username	Problem	Language	Result	Execution time	Memory
1083613		doducanh	Amusement Park (CEOI19_amusementpark)	C++14	100 / 100	2308 ms	2924 KiB

amusementpark

///breaker
#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
#define ii pair<int,int>
#define mp make_pair
#define in(x) freopen(x,"r",stdin)
#define out(x) freopen(x,"w",stdout)
#define bit(x,i) ((x>>i)&1)
#define lc (id<<1)
#define rc ((id<<1)^1)
const int mod=998244353;
bool independ[(1<<20)];
int a[20];
ll f[(1<<20)];
int nodeid[(1<<20)];
int n,m;
ll Pow(ll a,ll b)
{
    ll res=1;
    for(;b;b/=2,a=(a*a)%mod)if(b&1)res=(res*a)%mod;
    return res;
}
void sol(void){
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        int u,v;
        cin>>u>>v;
        u--;
        v--;
        a[u]|=(1<<v);
        a[v]|=(1<<u);
    }
    for(int i=0;i<n;i++)nodeid[(1<<i)]=i;
    independ[0]=1;
    for(int i=1;i<(1<<n);i++){
        if(independ[(i&(i-1))]&&(a[nodeid[(i&(-i))]]&(i&(i-1)))==0){
            independ[i]=1;
        }
    }
    f[0]=1;
    for(int i=1;i<(1<<n);i++){
        for(int j=i;j;j=((j-1)&i)){
            if(independ[j]){
                int tmp=(((__builtin_popcount(j)+1)&1)?-1:1);
                f[i]=(f[i]+tmp*f[i^j]+mod)%mod;
            }
        }
    }
    cout<<(1ll*m*f[(1<<n)-1]%mod*Pow(2,mod-2))%mod;
}
signed main(void)
{
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int t=1;
    while(t--){
        sol();
    }
    // you should actually read the stuff at the bottom
    return 0;
}
/* stuff you should look for
 * int overflow, array bounds
 * special cases (n=1?)
 * do smth instead of nothing and stay organized
 * WRITE STUFF DOWN
 * DON'T GET STUCK ON ONE APPROACH
 */

• Subtask 1: 7 / 7
• Subtask 2: 12 / 12
• Subtask 3: 23 / 23
• Subtask 4: 21 / 21
• Subtask 5: 37 / 37