Submission #1146563

#	Time	Username	Problem	Language	Result	Execution time	Memory
1146563		SmuggingSpun	Port Facility (JOI17_port_facility)	C++20	10 / 100	1 ms	328 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;
	}
}
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){
		sub2::solve();
	}
	else if(n <= 1000){
		sub2::solve();
	}
}

Compilation message (stderr)

port_facility.cpp: In function 'int main()':
port_facility.cpp:76:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   76 |                 freopen(taskname".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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