#include "islands.h"
#include <variant>
#include <algorithm>
#include <bitset>
#include <cstdint>
#include <cstring>
#include <iostream>
#include <limits.h>
#include <math.h>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
//#define int long long
#define loop(X, N) for(int X = 0; X < (N); X++)
#define all(V) V.begin(), V.end()
#define rall(V) V.rbegin(), V.rend()
using namespace std;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef uint64_t u64;
typedef int64_t i64;
int n, m;
vvii adj;
vb vis;
vi depths;
bool success = false;
int counter = 0;
vii inOut;
int dfs(int node, int d, int parent) {
if (node == parent) return 0;
if (vis[node]) {
return 1;
}
vis[node] = true;
depths[node] = d;
inOut[node].first = counter++;
int count = 0;
for (auto [child, idx] : adj[node]) {
if (child == parent) continue;
int res = dfs(child, d + 1, node);
count += res;
}
if (count >= 2)
success = true;
inOut[node].second = counter++;
return 1;
}
bool isAncestor(int a, int b) {
return inOut[a].first <= inOut[b].first && inOut[b].first <= inOut[a].second;
}
vi parents;
vi succesPath;
vi path;
int dfs2(int node, int parent, int edgeIdx) {
if (vis[node]) {
return 1;
}
parents[node] = parent;
vis[node] = true;
int count = 0;
vi validPaths;
for (auto [child, idx] : adj[node]) {
if (child == parent) continue;
path.push_back(idx);
int res = dfs2(child, node, idx);
path.pop_back();
if (res >= 1 && count < 2) {
count++;
validPaths.push_back(idx);
}
}
if (count >= 2 && !success) {
success = true;
succesPath = path;
succesPath.push_back(validPaths[0]);
succesPath.push_back(validPaths[0] ^ 1);
succesPath.push_back(validPaths[1]);
succesPath.push_back(validPaths[1] ^ 1);
succesPath.push_back(validPaths[0] ^ 1);
succesPath.push_back(validPaths[0]);
succesPath.push_back(validPaths[1] ^ 1);
succesPath.push_back(validPaths[1]);
for (int i = path.size() - 1; i >= 0; i++) {
succesPath.push_back(succesPath[i] ^ 1);
}
}
return 1;
}
std::variant<bool, std::vector<int>> find_journey(int N, int M, vi U, vi V) {
n = N;
m = M;
adj = vvii(n);
loop(i, m) {
adj[U[i]].push_back({V[i], i});
}
// if (n >= 3) {
// int n1 = adj[0][0].first;
// int n2 = adj[0][1].first;
// return vi{adj[0][0].second, adj[n1][0].second, adj[0][1].second, adj[n2][0].second, adj[n1][0].second, adj[0][0].second, adj[n2][0].second, adj[0][1].second };
// }
// return false;
depths = vi(n);
counter = 0;
inOut = vii(n);
vis = vb(n);
success = false;
parents = vi(n);
dfs2(0, -1, -1);
// vis = vb(n);
// marked = vi(n);
// dfs2(0);
if (success) {
return succesPath;
}
return false;
// return false;
// return success;
}
