#include "islands.h"
#include <bits/stdc++.h>
#include <variant>
using namespace std;
#define ll long long
variant<bool, std::vector<int>> find_journey(int n, int m, std::vector<int> u, std::vector<int> v) {
vector<vector<int>> adjlist(n);
map<pair<int, int>, int> edges;
for(int i = 0; i < m; i++) {
adjlist[u[i]].push_back(v[i]);
edges[make_pair(u[i], v[i])] = i;
}
vector<int> parent(n, -1);
vector<int> edgeUsed(n, -1);
vector<bool> vis(n, false);
queue<int> bfs;
bfs.push(0);
vis[0] = true;
while(!bfs.empty()) {
int curr = bfs.front(); bfs.pop();
int one = -1, two = -1;
for(auto i : adjlist[curr]) if(!vis[i]) {
if(one == -1) one = i;
else if(two == -1) {
two = i;
break;
}
}
if(two != -1) {
vector<int> order;
vector<int> ans;
int t1 = parent[curr];
int t2 = curr;
while(t2 != 0) {
order.push_back(edges[make_pair(t1, t2)]);
t1 = parent[t1];
t2 = parent[t2];
}
reverse(order.begin(), order.end());
for(auto i : order) ans.push_back(i);
int e0to1, e1to0, e0to2, e2to0;
e0to1 = edges[make_pair(curr, one)];
e1to0 = edges[make_pair(one, curr)];
e0to2 = edges[make_pair(curr, two)];
e2to0 = edges[make_pair(two, curr)];
vector<int> cancel({e0to1, e1to0, e0to2, e2to0, e1to0, e0to1, e2to0, e0to2});
for(auto i : cancel) ans.push_back(i);
reverse(order.begin(), order.end());
for(auto i : order) ans.push_back(i);
return ans;
} else if(one != -1) {
bfs.push(one);
parent[one] = curr;
vis[one] = true;
}
}
return false;
}
