CJANDDENISE (lqdoj) - Euler

#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pi32 = pair<int, int>;
using pi64 = pair<int64_t, int64_t>;
using ti32 = tuple<int, int, int>;
using ti64 = tuple<int64_t, int64_t, int64_t>;

const int N = 1e5 + 5;

int n, nE;
vector<pi32> graph[N];

bool visited[4 * N];
vector<int> path;

void Euler(int u) {
    while (!graph[u].empty()) {
        const auto [v, id] = graph[u].back(); graph[u].pop_back();
        if (!visited[id]) {
            visited[id] = true;
            Euler(v);
        }
    }

    path.push_back(u);
}

int main() {
#ifdef LOCAL
    freopen("in.txt", "r", stdin);
#else
    freopen("CJANDDENISEi.inp", "r", stdin);
    freopen("CJANDDENISE.out", "w", stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> n >> nE;

    for (int i = 1; i <= nE; i++) {
        int u, v; cin >> u >> v;
        graph[u].push_back({v, i});
        graph[v].push_back({u, i});
    }

    Euler(1);

    for (int u : path)
        cout << u << ' ';

    return 0;
}