#include "islands.h"
#include<bits/stdc++.h>
#include <variant>
#include <vector>
using namespace std;
// se 0 tem grau 2 -> ok
// se 0 tem grau 0 -> ruim
// se 0 tem grau 1
// se tem alguma backedge -> ok
// se tem alguem de grau 2 -> ok
// se nao -> ruim
const int N = 1010;
const int M = 200010;
vector <pair <int, int>> g[N];
int mark[M];
int mark_ver[N];
vector <int> res;
bool calc = false;
void app(vector <int> v){
for(auto x : v)
res.push_back(x);
return;
}
void dfs(int v, int p, int idx){
mark_ver[v] = 1;
mark[idx/2] = 1;
vector <int> cnt;
if(!calc) res.push_back(idx);
for(auto [x, i] : g[v]){
if(mark[i/2])
continue;
cnt.push_back(i);
if(cnt.size() > 1 and !calc){
calc = true;
vector <int> ap = res;
reverse(ap.begin(), ap.end());
int a = cnt[0], b = cnt[0]^1, c = cnt[1], d = cnt[1]^1;
app({a, b, c, d, b, a, d, c});
app(ap);
return;
}
}
for(auto [x, i] : g[v]){
if(mark[i/2])
continue;
dfs(x, v, i);
}
if(!calc) res.pop_back();
return;
}
std::variant<bool, std::vector<int>> find_journey(
int N, int m, std::vector<int> U, std::vector<int> V) {
for(int i = 0;i < m;i++){
g[U[i]].push_back({V[i], i});
}
if(g[0].size() >= 2){
int a = g[0][0].second, c = g[0][1].second;
int b = a^1, d = c^1;
app({a, b, c, d, b, a, d, c});
return res;
}
dfs(0, 0, M-1);
if(calc) return res;
return calc;
}
