LCA USING BINARY LIFTING

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

#define fast ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL)
#define ll long long
#define ld long double
#define pb push_back
#define fe first
#define se second
#define nl "\n"
#define pp pair < ll , ll >
#define sz(x) (ll)x.size()
#define st(x) sort(x.begin(),x.end())
#define rst(x) sort(x.rbegin(), x.rend())
#define all(x) x.begin(),x.end()
long double pi = 3.14159265358979323;

const double EPS = 1e-12;
const int N = 1e3 + 1;
const int mod = 1e9 + 7;

vector < ll > v[N];
ll level[N],dp[N][11],l;
bool vis[N];

void dfs(ll u , ll p){

    vis[u] = 1;
    dp[u][0] = p;
    for(int i = 1 ; i <= l ;i++ )
        dp[u][i] = dp[dp[u][i-1]][i-1];
    for(auto it : v[u]){
        if(!vis[it]){
            level[it] = level[u] + 1;
            dfs(it,u);
        }
    }
}
ll lca(ll u , ll v){
    if(level[u] < level[v])
        swap(u,v);
    ll diff = log2(level[u] - level[v]);
    for(int i = diff ; i >= 0 ; i-- ){
        if(level[u] != level[v])
            u = dp[u][i];
    }
    if(u == v)return u;
    diff = log2(level[v]);
    for(int i = diff ; i >= 0 ; i-- ){
        if(dp[u][i] != dp[v][i]){
            u = dp[u][i];
            v = dp[v][i];
        }
    }
    return dp[u][0];
}
int main()
{
    fast;
    ll t;
    cin >> t ;
  for(int i = 1 ; i  <= t ; i++ ){
        ll n;
        cin >> n ;
        l = log2(n);
        for(int i = 1 ; i  <= n ;  i++ ){
            ll m;
            cin >> m;
            while(m--){
                ll x;
                cin >> x ;
                v[i].pb(x);
                v[x].pb(i);
            }
        }
        dfs(1,1);
        ll q;
        cin >> q ;
        cout << "Case " << i << ":\n";
        while(q--){
            ll x , y;
            cin >> x >> y ;
            cout << lca(x,y) << "\n";
        }
        for(int i = 1 ; i  <= n ; i++ ){
            v[i].clear();
            vis[i] = 0 ;
            level[i] = 0 ;
            for(int j = 0  ; j < 11  ; j++ )
                dp[i][j]  = 0 ;
        }

    }





















    return 0;
        }