Submission #44586

#	Time	Username	Problem	Language	Result	Execution time	Memory
44586		ffresh	Port Facility (JOI17_port_facility)	C++17	0 / 100	2 ms	376 KiB

port_facility

#include <bits/stdc++.h>

using namespace std;

#define ll long long

const int N = 1e6+15,mod = 1e9+7;


int L[N],R[N];

int par[N],enemy[N];

int find(int a){
	if(a==-1)return -1;
	if(a==par[a])return a;
	return par[a]= find(par[a]);
}
void make_enemy(int a,int b){
	a = find(a),b = find(b);
	int u = find(enemy[a]), v = find(enemy[b]);
	if(a==b || (u!=-1 && u==v)){
		printf("0\n");
		exit(0);
	}
	if(v!=-1)par[v]= a;
	if(u!=-1)par[u]= b;
	enemy[a]= b;
	enemy[b]= a;
}


int main(){

    //freopen("input.txt","r",stdin);

    int n;
    cin>>n;
    vector<pair<int,int> >v;
    for(int i=1;i<=n;++i){
    	scanf("%d%d",&L[i],&R[i]);
    	v.push_back(make_pair(L[i],i));
    }
    sort(v.begin(),v.end());
    for(int i=1;i<=n;++i)par[i]= i,enemy[i]= -1;

   	set<pair<int,int> >s;
   	set<pair<int,int> >::iterator it,jt;
   	int u;
	for(int i=0;i<v.size();++i){

		int l = v[i].first, id = v[i].second;
		while(!s.empty()){
			it = s.begin();
			if( (*it).first<l)s.erase(it);
			else
				break;
		}
		pair<int,int> last= make_pair(-1,-1);
		bool is = 0;
		for(it = s.lower_bound(make_pair(l,0));it!= s.end();){
			if( (*it).first<=R[id]){
				u = (*it).second;

				make_enemy(u,id);
				last = *it;
				jt = it;
				++jt;
				s.erase(it);
				it = jt;
				is = 1;
			}
			else
				break;	 
		}
		if(is)
			s.insert(last);

		s.insert(make_pair(R[id],id));
	}
	long long ret= 1;
	for(int i=1;i<=n;++i){
		if(find(i)==i&& find(enemy[i])<i){
			ret= (ret*2)%mod;
		}
	}
	cout<<ret<<endl;

    return 0;
}

Compilation message (stderr)

port_facility.cpp: In function 'int main()':
port_facility.cpp:50:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<v.size();++i){
              ~^~~~~~~~~
port_facility.cpp:41:11: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
      scanf("%d%d",&L[i],&R[i]);
      ~~~~~^~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 12
• Subtask 3: 0 / 56
• Subtask 4: 0 / 22