LCA (SPOJ)

#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;


#define debug(x) cerr << '[' << (#x) << "] = " << x << '\n';

template<class T> using ordered_set = tree<T, null_type , less<T> , rb_tree_tag , tree_order_statistics_node_update> ;

const int maxn = 1005;
vector<int>g[maxn];
void PlayGround() {
    int N; cin >> N;
    for(int i=1; i<=N; ++i) {
        int m; cin >> m;
        while(m--) {
            int child; cin >> child;
            g[i].push_back(child);
            g[child].push_back(i);
        }
    }
    int l = 15;
    vector<vector<int>>up(N+5, vector<int>(l+1));
    vector<int>tin(N+5), tout(N+5);
    int timer = 0;
    function<void(int,int)> dfs = [&] (int node, int parent) {
        tin[node] = timer++;

        up[node][0] = parent;
        for(int i=1; i<=l; ++i)
            up[node][i] = up[up[node][i-1]][i-1];
        for(int child : g[node]) if(child != parent) {
            dfs(child, node);
        }

        tout[node] = timer++;
    };
    dfs(1, 1);
    auto isAncestor = [=] (int u, int v) {
        return tin[u] <= tin[v] && tout[u] >= tout[v];
    };
    auto getLCA = [=] (int u, int v) {
        if(isAncestor(u, v)) return u;
        if(isAncestor(v, u)) return v;
        for(int i=l; i>=0; --i) if(!isAncestor(up[u][i], v)) {
            u = up[u][i];
        }
        return up[u][0];
    };
    int q; cin >> q;
    while(q--) {
        int u, v; cin >> u >> v;
        cout << getLCA(u, v) << '\n';
    }
    for(int i=1; i<=N; ++i)
        g[i].clear();

    #ifndef ONLINE_JUDGE
        cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
    #endif
}
int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
    #endif
    int t; cin >> t;
    for(int i=1; i<=t; ++i) {
        cout << "Case " << i << ":\n";
        PlayGround();
    }

    return 0;
}