Distances

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t;
    cin >> t;
    while(t--)
    {
        int n;
        cin >> n;
        vector<int> v[n+1];
        for(int i=0;i<n-1;i++)
        {
            int a,b;
            cin >> a >> b;
            v[a].push_back(b);
            v[b].push_back(a);
        }
        vector<int> res;
        function<void(int,int,int)> dfs=[&](int a,int p,int d)
        {
            if((d%2)==0) res.push_back(a);
            for(int to:v[a])
            {
                if(to==p) continue;
                dfs(to,a,d+1);
            }
            if((d%2)==1) res.push_back(a);
        };
        dfs(1,0,0);
        for(int a:res) cout << a << " ";
        cout << "\n";
    }
    return 0;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED