Submission #1128823

#	Time	Username	Problem	Language	Result	Execution time	Memory
1128823		Rainmaker2627	Port Facility (JOI17_port_facility)	C++20	100 / 100	597 ms	126428 KiB

port_facility

#include<bits/stdc++.h>
using namespace std;
#define int long long

struct dsu {
	int n, cc;
	vector<int> r, s, d;

	dsu(int n) {
		this->n=n; cc=n;
		r.reserve(n+1);
		for (int i = 1; i <= n; ++i) r[i]=i;
		s.assign(n+1, 1);
		d.assign(n+1, 0);
	}

	int find(int a) {
		if (a==r[a]) return a;
		int p=find(r[a]);
		d[a]^=d[r[a]];
		return r[a]=p;
	}

	bool unite(int a, int b) {
		int ra=find(a), rb=find(b);
		if (ra==rb) return d[a]^d[b]==1;
		if (s[ra]<s[rb]) swap(ra, rb);
		d[rb]=1^d[a]^d[b];
		r[rb]=ra; s[ra]+=s[rb]; cc--;
		return true;
	}
};

int exp(int a, int b, int mod) {
	int x=1;
	while (b) {
		if (b%2) x=(x*a)%mod;
		a=(a*a)%mod; b/=2;
	} return x;
}

signed main() {
	cin.tie(0)->sync_with_stdio(false);

	int n;
	cin >> n;
	vector<pair<int, int>> s;
	vector<int> a(n), b(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i] >> b[i];
		s.push_back({a[i], i+1});
		s.push_back({b[i], -i-1});
	} sort(s.begin(), s.end());

	dsu uf(n+1);
	stack<list<int>> mt;
	for (auto i = 0; i < 2*n; ++i) {
		int j = s[i].second;
		if (j>0) {
			mt.push({});
			mt.top().push_back(j);
		} else {
			j=-j;
			list<int> tmp;
			while (true) {
				if (mt.top().back()==j) {
					mt.top().pop_back();
					if (mt.top().size()==0) mt.pop();
					break;
				}
				if (!uf.unite(j, mt.top().back())) { cout << "0\n"; return 0; }
				tmp.splice(tmp.begin(), mt.top());
				mt.pop();
			}
			if (tmp.size()) {
				mt.push({});
				mt.top().splice(mt.top().begin(), tmp);
			}
		}
	}

	cout << exp(2, uf.cc-1, 1e9+7) << '\n';
	return 0;
}

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