Submission #674068

#	Time	Username	Problem	Language	Result	Execution time	Memory
674068		US3RN4M3	Thousands Islands (IOI22_islands)	C++17	10.15 / 100	1085 ms	18460 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;
void dfs1(int cur) {
	vis[cur] = 1;
	for(auto [nxt, id] : fwd[cur]) {
		if(vis[nxt] == 0) dfs1(nxt);
		else if(vis[nxt] == 1) {
			is_cycle[cur] = true;
		}
	}
	vis[cur] = 2;
}
bool test(int bit) {
	{
		for(int i = 0; i < N; i++) vis[i] = 0;
		vector<int> q;
		for(auto [nxt, id] : fwd[0]) {
			if((id >> bit) & 1) continue;
			q.push_back(nxt);
			vis[nxt] = 1;
		}
		bool cond = false;
		int qidx = 0;
		while(qidx < q.size()) {
			int cur = q[qidx++];
			if(is_cycle[cur]) cond = true;
			for(auto [nxt, id] : fwd[cur]) {
				if(!vis[nxt]) {
					q.push_back(nxt);
					vis[nxt] = 1;
				}
			}
		}
		if(!cond) return false;
	}
	{
		for(int i = 0; i < N; i++) vis[i] = 0;
		vector<int> q;
		for(auto [nxt, id] : fwd[0]) {
			if(!((id >> bit) & 1)) continue;
			q.push_back(nxt);
			vis[nxt] = 1;
		}
		bool cond = false;
		int qidx = 0;
		while(qidx < q.size()) {
			int cur = q[qidx++];
			if(is_cycle[cur]) cond = true;
			for(auto [nxt, id] : fwd[cur]) {
				if(!vis[nxt]) {
					q.push_back(nxt);
					vis[nxt] = 1;
				}
			}
		}
		if(!cond) return false;
	}
	return true;
}
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});
	}
	dfs1(0);
	for(int bit = 0; bit < 20; bit++) {
		if(test(bit)) return vector<int>(1, 2);
	}
	return false;
}

Compilation message (stderr)

islands.cpp: In function 'bool test(int)':
islands.cpp:34:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 |   while(qidx < q.size()) {
      |         ~~~~~^~~~~~~~~~
islands.cpp:56:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 |   while(qidx < q.size()) {
      |         ~~~~~^~~~~~~~~~

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