Submission #1265826

#	Time	Username	Problem	Language	Result	Execution time	Memory
1265826		mhn_neek	Subtree (INOI20_subtree)	C++20	12 / 100	590 ms	1114112 KiB

Main

// IN THE NAME OF GOD
#include<bits/stdc++.h>
using namespace std;
typedef long long int lli;
typedef pair<lli,lli> pii;
typedef vector<lli> ve;
typedef vector<pii> vp;
const lli N = 5e5 + 100;
const lli mod = 1e9+7;
const lli INF = 1e18;
#define PB push_back
#define MP make_pair
#define fi first
#define se second
#define debug(x) cerr<<(#x)<<" "<<x<<endl
#define FOR(x,y) for(lli x = 0; x < y ;x++)
#define FORS(x,y) for(lli x = 1; x <= y ;x++)
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(),x.end()

struct DSU{
	lli par[N],rnk[N],sz[N];
	void build(lli X){
		FOR(i,X+4)
			par[i] = i,sz[i]= 1,rnk[i] = 0;
	}
	lli Find(lli u){
		return (par[u] == u ? u : par[u] = Find(par[u]));
	}
	void Merge(lli a,lli b){
		a = Find(a),b = Find(b);
		if(a==b)return;
		if(rnk[a] < rnk[b])swap(a,b);;
		rnk[a] = max(rnk[a],rnk[b]+1);
		sz[a] += sz[b];
		par[b] = a;
	}
};

lli n,m;
ve adj[N];
lli dp[N];
DSU dsu;

void dfs(lli u,lli par = 0){
	dp[u] = 1;
	for(lli v : adj[u]){
		if(v != par){
			dfs(v,u);
			dp[u] = dp[u]*(dp[v]+1)%mod;
		}
	}
}

int main(){
	ios_base::sync_with_stdio(false);cin.tie(0),cout.tie(0);
	cin>>n>>m;
	vp E;
	FOR(i,m){
		lli a,b;
		cin>>a>>b;
		adj[a].PB(b);
		adj[b].PB(a);
		E.PB(MP(a,b));
	}
	if(m > n-1){
		lli ans = 0;
		vector<bool> b(n,0);
		for(lli mask = 0; mask < (1<<n); mask ++){
			FOR(i,n)b[i] = 0;
			dsu.build(n);
			lli ver = -1;
			lli cnt = 0;
			FOR(i,n){
				lli p = (1<<i);
				if((mask&p) > 0)b[i] = 1,ver= i+1,cnt++;
			}
			if(ver == -1)continue;
			lli ec = 0;
			for(auto i : E){
				if(b[i.fi-1] && b[i.se-1]){
					dsu.Merge(i.fi,i.se);
					ec ++;
				}
			}
			if(dsu.sz[dsu.Find(ver)] == cnt && cnt == ec+1){
			ans ++;
			}


		}
		cout<<ans<<endl;
	}
	dfs(1);
	lli ans = 0;
	FORS(i,n)
		ans = (ans + dp[i])%mod;
	cout<<ans<<endl;

}

• Subtask 1: 0 / 8
• Subtask 2: 12 / 12
• Subtask 3: 0 / 30
• Subtask 4: 0 / 50