Distances

/*input
2
4
1 2
1 3
1 4
3
1 2
2 3
*/
#pragma GCC optimize ("O3")
#pragma GCC target ("avx2")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename X>
using ordered_map = tree<T, X, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename X>
using fast_map = cc_hash_table<T, X>;
//using ull = __uint128_t;
using ull = unsigned long long;
using ll = long long;
using ld = long double;
mt19937_64 rng(123);
const ll mod = 1000000007;
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin >> t;
	while (t--)
	{
		int n;
		cin >> n;
		vector<int>adj[n + 1];
		for (int i = 1; i < n; i++)
		{
			int a, b;
			cin >> a >> b;
			adj[a].push_back(b);
			adj[b].push_back(a);
		}
		function<vector<int>(int, int)> dfs = [&](int i, int p)
		{
			vector<int>c;
			for (int j : adj[i])
				if (j != p)
					c.push_back(j);
			if (c.size() == 0)
				return vector<int>({i});
			vector<int>ret;
			ret.push_back(i);
			for (int j : c)
			{
				vector<int>a = dfs(j, i);
				reverse(a.begin(), a.end());
				for (int v : a)
					ret.push_back(v);
			}
			return ret;
		};
		for (int i : dfs(1, 1))
			cout << i << " ";
		cout << "\n";
	}
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED