Submission #1146610

#	Time	Username	Problem	Language	Result	Execution time	Memory
1146610		SmuggingSpun	Port Facility (JOI17_port_facility)	C++20	78 / 100	354 ms	55516 KiB

port_facility

#include<bits/stdc++.h>
#define taskname "B"
using namespace std;
const int mod = 1e9 + 7;
int n;
namespace sub1{
	void solve(){
		vector<int>a(n), b(n), p(n << 1 | 1);
		for(int i = 0; i < n; i++){
			cin >> a[i] >> b[i];
			p[b[i]] = -(p[a[i]] = i + 1);
		}
		int ans = 1 << n;
		for(int mask = (1 << n) - 1; mask > -1; mask--){
			vector<stack<int>>st(2);
			for(int i = 1; i <= (n << 1); i++){
				bool bit = bool(mask >> (abs(p[i]) - 1) & 1);
				if(p[i] > 0){
					st[bit].push(p[i]);
				}
				else{
					if(st[bit].top() != -p[i]){
						ans--;
						break;
					}
					st[bit].pop();
				}
			}			
		}
		cout << ans;
	}
}
namespace sub2{
	void solve(){
		vector<int>a(n), b(n);
		vector<vector<int>>g(n);
		auto inside = [&] (int i, int l, int r){
			return l < i && r > i;		
		};
		for(int i = 0; i < n; i++){
			cin >> a[i] >> b[i];
			for(int j = 0; j < i; j++){
				if((inside(a[j], a[i], b[i]) && inside(b[i], a[j], b[j])) || (inside(a[i], a[j], b[j]) && inside(b[j], a[i], b[i]))){
					g[i].emplace_back(j);
					g[j].emplace_back(i);
				}
			}
		}
		vector<int>color(n, -1);
		int ans = 1;
		auto dfs = [&] (auto&& self, int s) -> void{
			for(int& d : g[s]){
				if(color[d] == -1){
					color[d] = color[s] ^ 1;
					self(self, d);
				}
				else if(color[s] == color[d]){
					cout << 0;
					exit(0);
				}
			}
		};
		for(int i = 0; i < n; i++){
			if(color[i] == -1){
				color[i] = 0;
				dfs(dfs, i);
				ans = (ans << 1) % mod;
			}
		}
		cout << ans;
	}
}
namespace sub34{
	const int lim = 1e6 + 5;
	int p[lim << 2], r[lim];
	int find_set(int N){
		return N == p[N] ? N : p[N] = find_set(p[N]);
	}
	void merge(int u, int v){
		p[find_set(u)] = find_set(v);
	}
	void solve(){
		memset(r, 0, sizeof(r));
		for(int i = 0; i < n; i++){
			int l;
			cin >> l >> r[l];
		}
		iota(p + 1, p + (n << 2) + 1, 1);
		set<int>s;
		for(int i = 1; i <= (n << 1); i++){
			if(r[i] > 0){
				for(auto it = s.lower_bound(i), bound_r = s.lower_bound(r[i]); it != bound_r; it = next(it)){
					merge(*it, r[i] + (n << 1));
					merge(*it + (n << 1), r[i]);
					if(find_set(*it) == find_set(*prev(bound_r))){
						break;
					}
				}
				s.insert(r[i]);
			}
		}
		int ans = 1;
		for(int i = 1; i <= (n << 1); i++){
			if(r[i] > 0){
				if(find_set(r[i]) == find_set(r[i] + (n << 1))){
					return void(cout << 0);
				}
				if(r[i] == find_set(r[i])){
					ans = (ans << 1) % mod;
				}
			}
		}
		cout << ans;
	}
}
int main(){
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	if(fopen(taskname".inp", "r")){
		freopen(taskname".inp", "r", stdin);
	}
	cin >> n;
	if(n <= 20){
		sub1::solve();
	}
	else if(n <= 2000){
		sub2::solve();
	}
	else{
		sub34::solve();
	}
}

Compilation message (stderr)

port_facility.cpp: In function 'int main()':
port_facility.cpp:119:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  119 |                 freopen(taskname".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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