Distances

//#pragma comment(linker, "/stack:200000000")
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

#define endl "\n"
#define all(c) (c).begin(),(c).end()

// if you're reading this i hope to meet you in IOI 2021
// RECHECK CONSTRAINTS AFTER MAKING A REDUCTION

void solve() {
	int n;
	cin >> n;
	vector<vector<int>> graph(n);
	for (int i = 0; i < n-1; i++) {
		int x, y;
		cin >> x >> y;
		x--, y--;
		graph[x].push_back(y);
		graph[y].push_back(x);
	}
	vector<int> res;
	function<void(int, int, bool)> dfs = [&](int v, int p, bool b) { // if b you end on root, if not you end one below root
		if (!b) res.push_back(v);
		for (int ne : graph[v]) if (ne != p) dfs(ne, v, !b);
		if (b) res.push_back(v);
	};
	dfs(0, 0, true);
	for (int e : res) cout << e+1 << " ";
	cout << endl;
}

signed main() {
	// freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
	std::ios::sync_with_stdio(false);
	cin.tie(0);
	
	int n;
	cin >> n;
	for (int i = 0; i < n; i++) solve();
}
/* --- PSolving ---
 * Simplifying (getting rid of variables, conditions, code logic, etc.)
 * Reframing
 * Solving a subtask (subgoal, aux. problem, removing a condition or fixing a parameter, etc.)
 * Inducing
 * Divide and conquer
 * Working backwards
 * Visual intuition
 * !! Reductions don't have to be specializations, they can be generalizations
 */

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED