12.bfs.cpp

 #include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>

#include <ext/pb_ds/tree_policy.hpp>

using namespace std;

using namespace __gnu_pbds;

template <class type1>

#define ll long long int

#define endl "\n"

#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>

using ordered_multiset = tree <type1, null_type, less_equal <type1>, rb_tree_tag, tree_order_statistics_node_update>;

 //ordered_multiset <ll> kek;(declaration for multiorder set)

// ordered_set o_set;(declaration)

//kek.order_of_key(i);(strictly less then i for multi order set)

//o_set.order_of_key(5) ;(strictly less then i for multi order set)

#define yes cout << "YES\n"

#define no cout << "NO\n"

vector<ll>adj[10000];

ll vis[10000];

ll level[10000];

void bfs(ll node)

{

     vis[node]=1;

     queue<ll>q;

     q.push(node);

     while(!q.empty())

     {

         ll par=q.front();

         q.pop();

         cout<<par<<" ";

         for(auto child:adj[par])

         {

             if(vis[child]==0)

             {

                vis[child]=1;

                q.push(child);

                level[child]=level[par]+1;

             }

         }

     }

}

int main()

{

    ios_base::sync_with_stdio(0);

    cin.tie(0);

    cout.tie(0);

   

    ll n,i;

    cin>>n;

    for(i=1;i<n;i++)

    {

         ll u,v;

         cin>>u>>v;

         adj[u].push_back(v);

         adj[v].push_back(u);

         

    }

    bfs(1);

    cout<<endl;

   for(i=1;i<=n;i++)

   {

     cout<<i<<" "<<level[i]<<endl;

   }

   

    return 0;

}