Submission #1225979

#	Time	Username	Problem	Language	Result	Execution time	Memory
1225979		_rain_	Port Facility (JOI17_port_facility)	C++20	100 / 100	963 ms	160928 KiB

port_facility

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;

const int MOD=1e9+7;
const int N=(int)1e6;
	int mul(int a,int b){
		return (LL)a*b%MOD;
	}

int n;
pair<int,int>p[N+2];

namespace subtask2{
	bool check(){
		return true;
	}
	
	const int LIMIT=2*N;
	
	int par[LIMIT+2],id[LIMIT+2],pre[LIMIT+2],nxt[LIMIT+2],v[LIMIT+2];
	
	int Find(int x){
		return par[x]==x?par[x]:par[x]=Find(par[x]);
	}
	
	vector<int>ke[LIMIT+2];
	void add_canh(int u,int v){
		ke[u].push_back(v),ke[v].push_back(u);
		return;
	}
	int vis[N+2];
	bool dfs(int u){
		for(auto&v:ke[u]){
			if (vis[v]==0){
				vis[v]=-vis[u];
				if (dfs(v)==false) return false;
			}
			else if (vis[u]==vis[v]) return false;
		}
		return true;
	}
	
	void main_code(){
		for(int i=1;i<=N+1;++i) par[i]=i,nxt[i]=i;
		for(int i=1;i<=n;++i) id[p[i].first]=id[p[i].second]=i;
		int cnt=0,comp=0;
		for(int i=1;i<=2*n;++i){
			if (id[i]==0) continue;
			if (pre[id[i]]==0) pre[id[i]]=++cnt,v[cnt]=id[i];
			else {
				int u=pre[id[i]];
				par[u]=Find(u+1);
				for(int j=par[u],k; j<=cnt;j=k){
					add_canh(v[j],id[i]);
					k=Find(nxt[j]+1);
					nxt[j]=cnt;
				}
			}
		}
		for(int i=1;i<=n;++i) if (vis[i]==0){
			vis[i]=1;
			if (dfs(i)) ++comp;
			else {
				cout<<0<<'\n';
				return;
			}
		}
		int ans=1;
		for(int i=1;i<=comp;++i) ans=mul(ans,2);
		cout<<ans<<'\n';
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0) ; cout.tie(0);
	#define task "main"
	if (fopen(task".inp","r")){
		freopen(task".inp","r",stdin);
		freopen(task".out","w",stdout);
	}
	
	cin>>n;
	for(int i=1;i<=n;++i) cin>>p[i].first>>p[i].second;
	return subtask2::main_code(),0;
	return 0;
}

Compilation message (stderr)

port_facility.cpp: In function 'int main()':
port_facility.cpp:80:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |                 freopen(task".inp","r",stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
port_facility.cpp:81:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |                 freopen(task".out","w",stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 12 / 12
• Subtask 3: 56 / 56
• Subtask 4: 22 / 22