TALCA-codechef-mr.convict

// Hack it and have it ;) //
/*author* Priyanshu Shrivastav (from IIT Palakkad) *
 * *_ __ ___  _ ______ ___  _ ____   ___  ___| |_  *
 * | '_ ` _ \| '__/ __/ _ \| '_ \ \ / / |/ __| __| *
 * | | | | | | | | (_| (_) | | | \ V /| | (__| |_  *
 * |_| |_| |_|_|(_)___\___/|_| |_|\_/ |_|\___|\__| *
When I wrote this, only God and I understood what I was doing
 ** * * * * * * * Now, only God knows!* * * * * * */
#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;

#ifndef CONVICTION
#pragma GCC       optimize ("Ofast")
#pragma GCC       optimize ("unroll-loops")
#pragma GCC       target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#endif

#define IOS       ios_base::sync_with_stdio(false); cin.tie (nullptr)
#define PREC      cout.precision (10); cout << fixed
#define x         first
#define y         second
#define fr(i,x,y) for (int i = x; i <= y; ++i)
#define fR(i,x,y) for (int i = x; i >= y; --i)
#define bg(x)     " [ " << #x << " : " << (x) << " ] "
#define un(x)     sort(x.begin(), x.end()), \
                  x.erase(unique(x.begin(), x.end()), x.end())

using   ll  =     long long;
using   ull =     unsigned long long;
using   ff  =     long double;
using   pii =     pair<int,int>;
using   pil =     pair<int,ll>;
typedef tree
< int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
ordered_set;

struct chash {
   int operator () (pii x) const { return x.x*31 + x.y; }
};
gp_hash_table <pii, int, chash> mp;

#if __cplusplus > 201103L
seed_seq seq{
   (uint64_t) chrono::duration_cast<chrono::nanoseconds>
      (chrono::high_resolution_clock::now().time_since_epoch()).count(),
      (uint64_t) __builtin_ia32_rdtsc(),
      (uint64_t) (uintptr_t) make_unique<char>().get()
};
mt19937 rng(seq); //uniform_int_distribution<int> (l, h)(rng); //[low, high]
#else
auto seed = chrono::high_resolution_clock::now().time_since_epoch().count();
mt19937 rng(seed);
#endif

#define debug(args...) { \
   /* WARNING : do NOT compile this debug func calls with following flags: // \
    * // -D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC -D_FORTIFY_SOURCE=2*/ \
   string _s = #args; replace(_s.begin(), _s.end(), ',', ' ');\
   stringstream _ss(_s); \
   istream_iterator<string> _it(_ss); err(_it, args); \
}
void err(istream_iterator<string> it) {
   it->empty(); cerr << " (Line : " << __LINE__ << ")" << '\n';
}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
   cerr << fixed << setprecision(15)
      << " [ " <<  *it << " : " << a  << " ] "<< ' ';
   err(++it, args...);
}
/*****************************************************************************/
//Don’t practice until you get it right. Practice until you can’t get it wrong

class LCA {
   public:
   int V;
   const int D = 21; // for handling n upto 2e6
   vector <vector <int>> table, dp;
   vector <int> depth;

   inline int walk(int u, int k) {
      for (int d = 0; d <= D && u != -1; ++d) {
         if ((1 << d) & k) {
            u = table[u][d];
         }
      }
      return u;
   }

   LCA(int n, vector <vector<pair <int, int>>> &T, int root = 0) {
      V = n;
      table.assign(n, vector <int>(D + 1, -1));
      dp.assign(n, vector <int>(D + 1, INT_MAX));
      depth.assign(n, 0);

      function <void(int, int, int)> dfs =
         [&](int u, int pr, int d) -> void {
            depth[u] = d;
            for (auto v_pair : T[u]) {
               int v = v_pair.first;
               int w = v_pair.second;
               if (v == pr) continue;
               table[v][0] = u;
               dp[v][0] = w;
               dfs(v, u, d + 1);
            }
         };

      dfs(root, -1, 0);

      for (int k = 1; k <= D; ++k) {
         for (int i = 0; i < n; ++i) {
            if (table[i][k - 1] == -1) continue;
            table[i][k] = table[table[i][k - 1]][k - 1];
            dp[i][k] = min(dp[i][k - 1], dp[table[i][k - 1]][k - 1]);
         }
      }
   }

   int find_lca(int u, int v) {
      if (depth[u] > depth[v]) {
         u = walk(u, depth[u] - depth[v]);
      }
      else if (depth[u] < depth[v]) {
         v = walk(v, depth[v] - depth[u]);
      }
      if (u == v) return u;

      for (int d = D; d >= 0; --d) {
         if (table[u][d] != table[v][d]) {
            u = table[u][d];
            v = table[v][d];
         }
      }
      return table[u][0];
   }
};

signed main() {
   IOS; PREC;

   int n;
   cin >> n;
   vector <vector<pii>> T(n, vector <pii>());
   for (int i = 0; i < n - 1; ++i) {
      int u, v; cin >> u >> v;
      --u, --v;
      T[u].push_back(make_pair(v, 1));
      T[v].push_back(make_pair(u, 1));
   }

   LCA solve(n, T);

   int q; cin >> q;
   while (q--){
      int r, x, y;
      cin >> r >> x >> y;
      --r, --x, --y;
      int z = solve.find_lca(x, y);

      int zr, xr, yr;
      zr = solve.find_lca(z, r);
      xr = solve.find_lca(x, r);
      yr = solve.find_lca(y, r);

      if (zr != z || (xr == z && yr == z)) {
         cout << z + 1 << '\n';
      }
      else {
         if (yr == z) cout << xr + 1 << '\n';
         else if (xr == z) cout << yr + 1 << '\n';
         else assert(false);
      }
   }

   return EXIT_SUCCESS;
}