Problem p02373 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <cassert>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

#define rep(i, a, n) for (int(i) = (a); (i) < (n); (i)++)
#define repq(i, a, n) for (int(i) = (a); (i) <= (n); (i)++)
#define repr(i, a, n) for (int(i) = (a); (i) >= (n); (i)--)
#define all(v) begin(v), end(v)
#define pb(a) push_back(a)
#define fr first
#define sc second
#define INF 2000000000
#define int long long int

#define X real()
#define Y imag()
#define EPS (1e-10)
#define EQ(a, b) (abs((a) - (b)) < EPS)
#define EQV(a, b) (EQ((a).X, (b).X) && EQ((a).Y, (b).Y))
#define LE(n, m) ((n) < (m) + EPS)
#define LEQ(n, m) ((n) <= (m) + EPS)
#define GE(n, m) ((n) + EPS > (m))
#define GEQ(n, m) ((n) + EPS >= (m))

typedef vector<int> VI;
typedef vector<VI> MAT;
typedef pair<int, int> pii;
typedef long long ll;

typedef complex<double> P;
typedef pair<P, P> L;
typedef pair<P, double> C;

int dy[] = {0, 0, 1, -1};
int dx[] = {1, -1, 0, 0};
int const MOD = 1000000007;

namespace std {
bool operator<(const P &a, const P &b) {
  return a.X != b.X ? a.X < b.X : a.Y < b.Y;
}
} // namespace std

// ?§?????????¨????????¨???????????????????¨???????????§???????
template <typename T> struct Edge {
  int from, to;
  T cost;
  Edge(int s, T d) : to(s), cost(d) {}
  Edge(int f, int s, T d) : from(f), to(s), cost(d) {}

  bool operator<(const Edge &e) const { return cost < e.cost; }
  bool operator>(const Edge &e) const { return cost > e.cost; }
};
#define Graph(type) vector<vector<Edge<type>>>

template <typename T> struct TreeLCA {
public:
  int const MAX_LOG_V;
  vector<vector<Edge<T>>> G;
  int root, vn;
  vector<vector<int>> parent;
  vector<int> depth;

  // constructor (Graph, root)
  TreeLCA(vector<vector<Edge<T>>> _G, int _r)
      : MAX_LOG_V(35), G(_G), root(_r), vn(G.size()),
        parent(MAX_LOG_V, vector<int>(vn, 0)), depth(vn, 0) {
    init(vn);
  }

  void dfs(int v, int p, int d) {
    parent[0][v] = p;
    depth[v] = d;
    for (int i = 0; i < G[v].size(); i++) {
      if (G[v][i].to != p)
        dfs(G[v][i].to, v, d + 1);
    }
  }

  void init(int V) {
    dfs(root, -1, 0);
    for (int k = 0; k + 1 < MAX_LOG_V; k++) {
      for (int v = 0; v < V; v++) {
        if (parent[k][v] < 0)
          parent[k + 1][v] = -1;
        else
          parent[k + 1][v] = parent[k][parent[k][v]];
      }
    }
  }

  int solve(int u, int v) {
    if (depth[u] > depth[v])
      swap(u, v);
    for (int k = 0; k < MAX_LOG_V; k++) {
      if ((depth[v] - depth[u]) >> k & 1) {
        v = parent[k][v];
      }
    }
    if (u == v)
      return u;
    for (int k = MAX_LOG_V - 1; k >= 0; k--) {
      if (parent[k][u] != parent[k][v]) {
        u = parent[k][u];
        v = parent[k][v];
      }
    }
    return parent[0][u];
  }
};

signed main() {
  int n, k, c;
  cin >> n;
  Graph(int) G(n);
  rep(i, 0, n) {
    cin >> k;
    rep(j, 0, k) {
      cin >> c;
      G[i].pb(Edge<int>(c, 1));
    }
  }

  TreeLCA<int> tr(G, 0);
  int q;
  cin >> q;
  int u, v;
  rep(i, 0, q) {
    cin >> u >> v;
    cout << tr.solve(u, v) << endl;
  }
  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cassert>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

#define rep(i, a, n) for (int(i) = (a); (i) < (n); (i)++)
#define repq(i, a, n) for (int(i) = (a); (i) <= (n); (i)++)
#define repr(i, a, n) for (int(i) = (a); (i) >= (n); (i)--)
#define all(v) begin(v), end(v)
#define pb(a) push_back(a)
#define fr first
#define sc second
#define INF 2000000000
#define int long long int

#define X real()
#define Y imag()
#define EPS (1e-10)
#define EQ(a, b) (abs((a) - (b)) < EPS)
#define EQV(a, b) (EQ((a).X, (b).X) && EQ((a).Y, (b).Y))
#define LE(n, m) ((n) < (m) + EPS)
#define LEQ(n, m) ((n) <= (m) + EPS)
#define GE(n, m) ((n) + EPS > (m))
#define GEQ(n, m) ((n) + EPS >= (m))

typedef vector<int> VI;
typedef vector<VI> MAT;
typedef pair<int, int> pii;
typedef long long ll;

typedef complex<double> P;
typedef pair<P, P> L;
typedef pair<P, double> C;

int dy[] = {0, 0, 1, -1};
int dx[] = {1, -1, 0, 0};
int const MOD = 1000000007;

namespace std {
bool operator<(const P &a, const P &b) {
  return a.X != b.X ? a.X < b.X : a.Y < b.Y;
}
} // namespace std

// ?§?????????¨????????¨???????????????????¨???????????§???????
template <typename T> struct Edge {
  int from, to;
  T cost;
  Edge(int s, T d) : to(s), cost(d) {}
  Edge(int f, int s, T d) : from(f), to(s), cost(d) {}

  bool operator<(const Edge &e) const { return cost < e.cost; }
  bool operator>(const Edge &e) const { return cost > e.cost; }
};
#define Graph(type) vector<vector<Edge<type>>>

template <typename T> struct TreeLCA {
public:
  int const MAX_LOG_V;
  vector<vector<Edge<T>>> G;
  int root, vn;
  vector<vector<int>> parent;
  vector<int> depth;

  // constructor (Graph, root)
  TreeLCA(vector<vector<Edge<T>>> _G, int _r)
      : MAX_LOG_V(35), G(_G), root(_r), vn(G.size()),
        parent(MAX_LOG_V, vector<int>(vn, 0)), depth(vn, 0) {}

  void dfs(int v, int p, int d) {
    parent[0][v] = p;
    depth[v] = d;
    for (int i = 0; i < G[v].size(); i++) {
      if (G[v][i].to != p)
        dfs(G[v][i].to, v, d + 1);
    }
  }

  void init(int V) {
    dfs(root, -1, 0);
    for (int k = 0; k + 1 < MAX_LOG_V; k++) {
      for (int v = 0; v < V; v++) {
        if (parent[k][v] < 0)
          parent[k + 1][v] = -1;
        else
          parent[k + 1][v] = parent[k][parent[k][v]];
      }
    }
  }

  int solve(int u, int v) {
    init(vn);
    if (depth[u] > depth[v])
      swap(u, v);
    for (int k = 0; k < MAX_LOG_V; k++) {
      if ((depth[v] - depth[u]) >> k & 1) {
        v = parent[k][v];
      }
    }
    if (u == v)
      return u;
    for (int k = MAX_LOG_V - 1; k >= 0; k--) {
      if (parent[k][u] != parent[k][v]) {
        u = parent[k][u];
        v = parent[k][v];
      }
    }
    return parent[0][u];
  }
};

signed main() {
  int n, k, c;
  cin >> n;
  Graph(int) G(n);
  rep(i, 0, n) {
    cin >> k;
    rep(j, 0, k) {
      cin >> c;
      G[i].pb(Edge<int>(c, 1));
    }
  }

  TreeLCA<int> tr(G, 0);
  int q;
  cin >> q;
  int u, v;
  rep(i, 0, q) {
    cin >> u >> v;
    cout << tr.solve(u, v) << endl;
  }
  return 0;
}