Submission #1042575

#	Time	Username	Problem	Language	Result	Execution time	Memory
1042575		Alihan_8	Thousands Islands (IOI22_islands)	C++17	24 / 100	67 ms	13952 KiB

islands

#include "islands.h"

#include <variant>
#include <vector>

#include <bits/stdc++.h>

using namespace std;

#define pb push_back
#define ar array
#define all(x) x.begin(), x.end()
#define ln '\n';

template <class F, class S>
bool chmin(F &u, const S &v){
	bool flag = false;
	
	if ( u > v ){
		u = v; flag |= true;
	}
	
	return flag;
}

std::variant<bool, std::vector<int>> find_journey(
    int N, int M, std::vector<int> U, std::vector<int> V) {
  
	int n = N, m = M;
	
	// subtask #4
	
	vector <vector<int>> adj(n);
	
	map <pair<int,int>,vector<int>> id;
	
	for ( int i = 0; i < m; i++ ){
		if ( i % 2 == 0 ){
			adj[U[i]].pb(V[i]);
		}
		
		id[{U[i], V[i]}].pb(i);
	}
	
	vector <int> us(n), path, a;
	
	int sx = -1;
	
	auto dfs = [&](auto dfs, int u) -> void{
		if ( sx != -1 ) return;
		
		path.pb(u);
		us[u] = 1;
		
		for ( auto &v: adj[u] ){
			if ( sx != -1 ) return;
			
			if ( !us[v] ){
				dfs(dfs, v);
			} else if ( us[v] == 1 ){ // cycle found
				 sx = v; a = path;
				 
				 return;
			}
		}
		
		path.pop_back();
		us[u] = 2;
	};
	
	dfs(dfs, 0);
	
	if ( sx == -1 ){
		return false;
	}
	
	vector <int> ans;
	
	int s = a.size(), j = -1;
	
	for ( int i = 0; i < s; i++ ){
		if ( a[i] == sx ){
			j = i; break;
		}
		
		assert(i + 1 < s);
		
		ans.pb(id[{a[i], a[i + 1]}][0]);
    }
	
	vector <int> tmp;
	
	for ( int i = j; i < s; i++ ){
		int nxt = (i + 1 < s ? i + 1 : j);
		
		ans.pb(id[{a[i], a[nxt]}][0]);
	}
	
	for ( int i = j; i < s; i++ ){
		int nxt = (i + 1 < s ? i + 1 : j);
		
		ans.pb(id[{a[i], a[nxt]}][1]);
	}
	
	for ( int i = s - 1; i >= j; i-- ){
		int nxt = (i + 1 < s ? i + 1 : j);
		
		ans.pb(id[{a[i], a[nxt]}][0]);
	}
	
	for ( int i = s - 1; i >= j; i-- ){
		int nxt = (i + 1 < s ? i + 1 : j);
		
		ans.pb(id[{a[i], a[nxt]}][1]);
	}
	
	for ( int i = j - 1; i >= 0; i-- ){
		ans.pb(id[{a[i], a[i + 1]}][0]);
	}
	
	return ans;
}

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