Submission #674071

#	Time	Username	Problem	Language	Result	Execution time	Memory
674071		US3RN4M3	Thousands Islands (IOI22_islands)	C++17	11.90 / 100	52 ms	18188 KiB

islands

#include"islands.h"
#include<vector>
#include<algorithm>
#include<iostream>
using namespace std;
using ll = long long;
const int mx = 200005;
vector<pair<int, int>> fwd[mx];
vector<pair<int, int>> bck[mx];
int vis[mx];
bool is_cycle[mx];
int N;
int bit;
bool toggle;
bool has_cycle(int cur) {
	vis[cur] = 1;
	for(auto [nxt, id] : fwd[cur]) {
		if(cur == 0) {
			if(toggle) {
				if((id >> bit) & 1) continue;
			} else {
				if(!((id >> bit) & 1)) continue;
			}
		}
		if(vis[nxt] == 0) {
			if(has_cycle(nxt)) return true;
		} else if(vis[nxt] == 1) {
			return true;
		}
	}
	vis[cur] = 2;
	return false;
}
std::variant<bool, std::vector<int>> find_journey(int _N, int M, std::vector<int> U, std::vector<int> V) {
	N = _N;
	for(int i = 0; i < N; i++) {
		fwd[i].clear();
		bck[i].clear();
		vis[i] = 0;
	}
	for(int i = 0; i < M; i++) {
		fwd[U[i]].push_back({V[i], i});
		bck[V[i]].push_back({U[i], i});
	}
	for(bit = 0; bit < 20; bit++) {
		for(int i = 0; i < N; i++) vis[i] = 0;
		toggle = false;
		if(!has_cycle(0)) continue;
		for(int i = 0; i < N; i++) vis[i] = 0;
		toggle = true;
		if(!has_cycle(0)) continue;
		return vector<int>(1, 2);
	}
	return false;
}

• Subtask 1: 1.75 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 0 / 21
• Subtask 4: 8.399999999999999 / 24
• Subtask 5: 0 / 45