Problem p02373 (C++) — buggy submission, verdict: Runtime Error

// need
#include <algorithm>
#include <iostream>

// data structure
#include <bitset>
// #include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
// #include <array>
// #include <tuple>
#include <complex>
#include <unordered_map>
#include <unordered_set>
// #include <deque>
#include <valarray>

// stream
// #include <istream>
// #include <sstream>
// #include <ostream>

// etc
#include <cassert>
#include <functional>
#include <iomanip>
// #include <typeinfo>
#include <chrono>
#include <numeric>
#include <random>

#define INIT                                                                   \\
  std::ios::sync_with_stdio(false);                                            \\
  std::cin.tie(0);
#define VAR(type, ...)                                                         \\
  type __VA_ARGS__;                                                            \\
  MACRO_VAR_Scan(__VA_ARGS__);
template <typename T> void MACRO_VAR_Scan(T &t) { std::cin >> t; }
template <typename First, typename... Rest>
void MACRO_VAR_Scan(First &first, Rest &...rest) {
  std::cin >> first;
  MACRO_VAR_Scan(rest...);
}
#define VEC_ROW(type, n, ...)                                                  \\
  std::vector<type> __VA_ARGS__;                                               \\
  MACRO_VEC_ROW_Init(n, __VA_ARGS__);                                          \\
  for (int i = 0; i < n; ++i) {                                                \\
    MACRO_VEC_ROW_Scan(i, __VA_ARGS__);                                        \\
  }
template <typename T> void MACRO_VEC_ROW_Init(int n, T &t) { t.resize(n); }
template <typename First, typename... Rest>
void MACRO_VEC_ROW_Init(int n, First &first, Rest &...rest) {
  first.resize(n);
  MACRO_VEC_ROW_Init(n, rest...);
}
template <typename T> void MACRO_VEC_ROW_Scan(int p, T &t) { std::cin >> t[p]; }
template <typename First, typename... Rest>
void MACRO_VEC_ROW_Scan(int p, First &first, Rest &...rest) {
  std::cin >> first[p];
  MACRO_VEC_ROW_Scan(p, rest...);
}
#define OUT(d) std::cout << d;
#define FOUT(n, d) std::cout << std::fixed << std::setprecision(n) << d;
#define SOUT(n, c, d) std::cout << std::setw(n) << std::setfill(c) << d;
#define SP std::cout << " ";
#define TAB std::cout << "\\t";
#define BR std::cout << "\\n";
#define ENDL std::cout << std::endl;
#define FLUSH std::cout << std::flush;
#define VEC(type, c, n)                                                        \\
  std::vector<type> c(n);                                                      \\
  for (auto &i : c)                                                            \\
    std::cin >> i;
#define MAT(type, c, m, n)                                                     \\
  std::vector<std::vector<type>> c(m, std::vector<type>(n));                   \\
  for (auto &r : c)                                                            \\
    for (auto &i : r)                                                          \\
      std::cin >> i;
#define ALL(a) (a).begin(), (a).end()
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define RFOR(i, a, b) for (int i = (b)-1; i >= (a); --i)
#define REP(i, n) for (int i = 0; i < int(n); ++i)
#define RREP(i, n) for (int i = (n)-1; i >= 0; --i)
#define FORLL(i, a, b) for (ll i = ll(a); i < ll(b); ++i)
#define RFORLL(i, a, b) for (ll i = ll(b) - 1; i >= ll(a); --i)
#define REPLL(i, n) for (ll i = 0; i < ll(n); ++i)
#define RREPLL(i, n) for (ll i = ll(n) - 1; i >= 0; --i)
#define PAIR std::pair<int, int>
#define PAIRLL std::pair<ll, ll>
#define IN(a, x, b) (a <= x && x < b)
#define SHOW(d)                                                                \\
  { std::cerr << #d << "\\t:" << d << "\\n"; }
#define SHOWVECTOR(v)                                                          \\
  {                                                                            \\
    std::cerr << #v << "\\t:";                                                  \\
    for (const auto &xxx : v) {                                                \\
      std::cerr << xxx << " ";                                                 \\
    }                                                                          \\
    std::cerr << "\\n";                                                         \\
  }
#define SHOWVECTOR2(v)                                                         \\
  {                                                                            \\
    std::cerr << #v << "\\t:\\n";                                                \\
    for (const auto &xxx : v) {                                                \\
      for (const auto &yyy : xxx) {                                            \\
        std::cerr << yyy << " ";                                               \\
      }                                                                        \\
      std::cerr << "\\n";                                                       \\
    }                                                                          \\
  }
#define SHOWPAIR(p)                                                            \\
  { std::cerr << #p << "\\t:(" << p.first << ",\\t" << p.second << ")\\n"; }
#define SHOWPAIRVECTOR2(v)                                                     \\
  {                                                                            \\
    std::cerr << #v << "\\t:\\n";                                                \\
    for (const auto &xxx : v) {                                                \\
      for (const auto &yyy : xxx) {                                            \\
        std::cerr << '(' << yyy.first << ", " << yyy.second << ") ";           \\
      }                                                                        \\
      std::cerr << "\\n";                                                       \\
    }                                                                          \\
  }
#define SHOWPAIRVECTOR(v)                                                      \\
  {                                                                            \\
    for (const auto &xxx : v) {                                                \\
      std::cerr << '(' << xxx.first << ", " << xxx.second << ") ";             \\
    }                                                                          \\
    std::cerr << "\\n";                                                         \\
  }
#define SHOWQUEUE(a)                                                           \\
  {                                                                            \\
    std::queue<decltype(a.front())> tmp(a);                                    \\
    std::cerr << #a << "\\t:";                                                  \\
    for (int i = 0; i < static_cast<int>(a.size()); ++i) {                     \\
      std::cerr << tmp.front() << "\\n";                                        \\
      tmp.pop();                                                               \\
    }                                                                          \\
    std::cerr << "\\n";                                                         \\
  }
template <typename T> inline T CHMAX(T &a, const T b) {
  return a = (a < b) ? b : a;
}
template <typename T> inline T CHMIN(T &a, const T b) {
  return a = (a > b) ? b : a;
}
#define EXCEPTION(msg)                                                         \\
  throw std::string("Exception : " msg " [ in ") + __func__ + " : " +          \\
      std::to_string(__LINE__) + " lines ]"
#define TRY(cond, msg)                                                         \\
  try {                                                                        \\
    if (cond)                                                                  \\
      EXCEPTION(msg);                                                          \\
  } catch (std::string s) {                                                    \\
    std::cerr << s << std::endl;                                               \\
  }
void CHECKTIME(std::function<void()> f) {
  auto start = std::chrono::system_clock::now();
  f();
  auto end = std::chrono::system_clock::now();
  auto res = std::chrono::duration_cast<std::chrono::nanoseconds>((end - start))
                 .count();
  std::cerr << "[Time:" << res << "ns  (" << res / (1.0e9) << "s)]\\n";
}

#define int ll
using ll = long long;
using ull = unsigned long long;
constexpr int INFINT = 1 << 30;                         // 1.07x10^ 9
constexpr int INFINT_LIM = (1LL << 31) - 1;             // 2.15x10^ 9
constexpr ll INFLL = 1LL << 60;                         // 1.15x10^18
constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62); // 9.22x10^18
constexpr double EPS = 1e-7;
constexpr int MOD = 1000000007;
constexpr double PI = 3.141592653589793238462643383279;

class LCA {
private:
  const std::vector<std::vector<int>> &graph; // graph's list expression
  int root;
  int n;     // the number of nodes
  int log2n; // = floor(log2(n))
  std::vector<std::vector<int>>
      parent; // parent[x][v] = a parent(above 2^x) of v (nonexistence -> -1)
  std::vector<int> depth; // the depth of each node

public:
  LCA(const std::vector<std::vector<int>> &graph, int root)
      : graph(graph), root(root), n(graph.size()),
        log2n(std::floor(std::log2(n) + 1)),
        parent(log2n, std::vector<int>(n, 0)), depth(n, 0) {
    init();
  }

  // Check the depth of each node(node "v" -> parent is "p", depth is "d")
  void dfs(int v, int p, int d) {
    std::stack<int> stack;
    stack.push(v);
    parent[0][v] = p;
    depth[v] = d;
    while (!stack.empty()) {
      int now = stack.top();
      stack.pop();
      for (int i = 0; i < graph[now].size(); ++i) {
        int to = graph[now][i];
        if (to == parent[0][now])
          continue;
        parent[0][to] = now;
        depth[to] = depth[now] + 1;
        stack.push(to); // Check each child of v
      }
    }
  }

  // Initialize
  void init() {
    // Initialize "parent[0]" and "depth"
    dfs(root, -1, 0);

    // Initialize "parent"
    for (int k = 0; k < log2n - 1; ++k) {
      for (int v = 0; v < n; ++v) {
        if (parent[k][v] < 0) { // If parent above 2^k of v is nonexistence
          parent[k + 1][v] = -1;
        } else {
          parent[k + 1][v] = parent[k][parent[k][v]];
        }
      }
    }
  }

  // Find LCA of (u, v)
  int lca(int u, int v) {
    // go up parent while depth of u and v is same
    if (depth[u] > depth[v])
      std::swap(u, v);
    for (int k = 0; k < log2n; ++k) {
      if ((depth[v] - depth[u]) >> k & 1) {
        v = parent[k][v]; // go up to 2^k if k-th binary is 1
      }
    }

    if (u == v)
      return u; // this case is that v is in u's subtree

    // Find LCA by binary searching
    for (int k = log2n - 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() {
  INIT;
  VAR(int, n);
  std::vector<std::vector<int>> g(n);
  REP(i, n) {
    VAR(int, k);
    VEC(int, c, k);
    REP(j, k) { g[i].emplace_back(c[j]); }
  }
  LCA lca(g, 0);
  VAR(int, Q);
  REP(q, Q) {
    VAR(int, u, v);
    OUT(lca.lca(u, v)) BR;
  }
  return 0;
}

Error: 0

Fixed submission:

// need
#include <algorithm>
#include <iostream>

// data structure
#include <bitset>
// #include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
// #include <array>
// #include <tuple>
#include <complex>
#include <unordered_map>
#include <unordered_set>
// #include <deque>
#include <valarray>

// stream
// #include <istream>
// #include <sstream>
// #include <ostream>

// etc
#include <cassert>
#include <functional>
#include <iomanip>
// #include <typeinfo>
#include <chrono>
#include <numeric>
#include <random>

#define INIT                                                                   \\
  std::ios::sync_with_stdio(false);                                            \\
  std::cin.tie(0);
#define VAR(type, ...)                                                         \\
  type __VA_ARGS__;                                                            \\
  MACRO_VAR_Scan(__VA_ARGS__);
template <typename T> void MACRO_VAR_Scan(T &t) { std::cin >> t; }
template <typename First, typename... Rest>
void MACRO_VAR_Scan(First &first, Rest &...rest) {
  std::cin >> first;
  MACRO_VAR_Scan(rest...);
}
#define VEC_ROW(type, n, ...)                                                  \\
  std::vector<type> __VA_ARGS__;                                               \\
  MACRO_VEC_ROW_Init(n, __VA_ARGS__);                                          \\
  for (int i = 0; i < n; ++i) {                                                \\
    MACRO_VEC_ROW_Scan(i, __VA_ARGS__);                                        \\
  }
template <typename T> void MACRO_VEC_ROW_Init(int n, T &t) { t.resize(n); }
template <typename First, typename... Rest>
void MACRO_VEC_ROW_Init(int n, First &first, Rest &...rest) {
  first.resize(n);
  MACRO_VEC_ROW_Init(n, rest...);
}
template <typename T> void MACRO_VEC_ROW_Scan(int p, T &t) { std::cin >> t[p]; }
template <typename First, typename... Rest>
void MACRO_VEC_ROW_Scan(int p, First &first, Rest &...rest) {
  std::cin >> first[p];
  MACRO_VEC_ROW_Scan(p, rest...);
}
#define OUT(d) std::cout << d;
#define FOUT(n, d) std::cout << std::fixed << std::setprecision(n) << d;
#define SOUT(n, c, d) std::cout << std::setw(n) << std::setfill(c) << d;
#define SP std::cout << " ";
#define TAB std::cout << "\\t";
#define BR std::cout << "\\n";
#define ENDL std::cout << std::endl;
#define FLUSH std::cout << std::flush;
#define VEC(type, c, n)                                                        \\
  std::vector<type> c(n);                                                      \\
  for (auto &i : c)                                                            \\
    std::cin >> i;
#define MAT(type, c, m, n)                                                     \\
  std::vector<std::vector<type>> c(m, std::vector<type>(n));                   \\
  for (auto &r : c)                                                            \\
    for (auto &i : r)                                                          \\
      std::cin >> i;
#define ALL(a) (a).begin(), (a).end()
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define RFOR(i, a, b) for (int i = (b)-1; i >= (a); --i)
#define REP(i, n) for (int i = 0; i < int(n); ++i)
#define RREP(i, n) for (int i = (n)-1; i >= 0; --i)
#define FORLL(i, a, b) for (ll i = ll(a); i < ll(b); ++i)
#define RFORLL(i, a, b) for (ll i = ll(b) - 1; i >= ll(a); --i)
#define REPLL(i, n) for (ll i = 0; i < ll(n); ++i)
#define RREPLL(i, n) for (ll i = ll(n) - 1; i >= 0; --i)
#define PAIR std::pair<int, int>
#define PAIRLL std::pair<ll, ll>
#define IN(a, x, b) (a <= x && x < b)
#define SHOW(d)                                                                \\
  { std::cerr << #d << "\\t:" << d << "\\n"; }
#define SHOWVECTOR(v)                                                          \\
  {                                                                            \\
    std::cerr << #v << "\\t:";                                                  \\
    for (const auto &xxx : v) {                                                \\
      std::cerr << xxx << " ";                                                 \\
    }                                                                          \\
    std::cerr << "\\n";                                                         \\
  }
#define SHOWVECTOR2(v)                                                         \\
  {                                                                            \\
    std::cerr << #v << "\\t:\\n";                                                \\
    for (const auto &xxx : v) {                                                \\
      for (const auto &yyy : xxx) {                                            \\
        std::cerr << yyy << " ";                                               \\
      }                                                                        \\
      std::cerr << "\\n";                                                       \\
    }                                                                          \\
  }
#define SHOWPAIR(p)                                                            \\
  { std::cerr << #p << "\\t:(" << p.first << ",\\t" << p.second << ")\\n"; }
#define SHOWPAIRVECTOR2(v)                                                     \\
  {                                                                            \\
    std::cerr << #v << "\\t:\\n";                                                \\
    for (const auto &xxx : v) {                                                \\
      for (const auto &yyy : xxx) {                                            \\
        std::cerr << '(' << yyy.first << ", " << yyy.second << ") ";           \\
      }                                                                        \\
      std::cerr << "\\n";                                                       \\
    }                                                                          \\
  }
#define SHOWPAIRVECTOR(v)                                                      \\
  {                                                                            \\
    for (const auto &xxx : v) {                                                \\
      std::cerr << '(' << xxx.first << ", " << xxx.second << ") ";             \\
    }                                                                          \\
    std::cerr << "\\n";                                                         \\
  }
#define SHOWQUEUE(a)                                                           \\
  {                                                                            \\
    std::queue<decltype(a.front())> tmp(a);                                    \\
    std::cerr << #a << "\\t:";                                                  \\
    for (int i = 0; i < static_cast<int>(a.size()); ++i) {                     \\
      std::cerr << tmp.front() << "\\n";                                        \\
      tmp.pop();                                                               \\
    }                                                                          \\
    std::cerr << "\\n";                                                         \\
  }
template <typename T> inline T CHMAX(T &a, const T b) {
  return a = (a < b) ? b : a;
}
template <typename T> inline T CHMIN(T &a, const T b) {
  return a = (a > b) ? b : a;
}
#define EXCEPTION(msg)                                                         \\
  throw std::string("Exception : " msg " [ in ") + __func__ + " : " +          \\
      std::to_string(__LINE__) + " lines ]"
#define TRY(cond, msg)                                                         \\
  try {                                                                        \\
    if (cond)                                                                  \\
      EXCEPTION(msg);                                                          \\
  } catch (std::string s) {                                                    \\
    std::cerr << s << std::endl;                                               \\
  }
void CHECKTIME(std::function<void()> f) {
  auto start = std::chrono::system_clock::now();
  f();
  auto end = std::chrono::system_clock::now();
  auto res = std::chrono::duration_cast<std::chrono::nanoseconds>((end - start))
                 .count();
  std::cerr << "[Time:" << res << "ns  (" << res / (1.0e9) << "s)]\\n";
}

#define int ll
using ll = long long;
using ull = unsigned long long;
constexpr int INFINT = 1 << 30;                         // 1.07x10^ 9
constexpr int INFINT_LIM = (1LL << 31) - 1;             // 2.15x10^ 9
constexpr ll INFLL = 1LL << 60;                         // 1.15x10^18
constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62); // 9.22x10^18
constexpr double EPS = 1e-7;
constexpr int MOD = 1000000007;
constexpr double PI = 3.141592653589793238462643383279;

class LCA {
private:
  const std::vector<std::vector<int>> &graph; // graph's list expression
  int root;
  int n;     // the number of nodes
  int log2n; // = floor(log2(n))
  std::vector<std::vector<int>>
      parent; // parent[x][v] = a parent(above 2^x) of v (nonexistence -> -1)
  std::vector<int> depth; // the depth of each node

public:
  LCA(const std::vector<std::vector<int>> &graph, int root)
      : graph(graph), root(root), n(graph.size()),
        log2n(std::max((signed)std::floor(std::log2(n)), 1)),
        parent(log2n, std::vector<int>(n, 0)), depth(n, 0) {
    init();
  }

  // Check the depth of each node(node "v" -> parent is "p", depth is "d")
  void dfs(int v, int p, int d) {
    parent[0][v] = p;
    depth[v] = d;
    for (int i = 0; i < graph[v].size(); ++i) {
      if (graph[v][i] != p) {
        dfs(graph[v][i], v, d + 1); // Check each child of v
      }
    }
  }

  // Initialize
  void init() {
    // Initialize "parent[0]" and "depth"
    dfs(root, -1, 0);

    // Initialize "parent"
    for (int k = 0; k < log2n - 1; ++k) {
      for (int v = 0; v < n; ++v) {
        if (parent[k][v] < 0) { // If parent above 2^k of v is nonexistence
          parent[k + 1][v] = -1;
        } else {
          parent[k + 1][v] = parent[k][parent[k][v]];
        }
      }
    }
  }

  // Find LCA of (u, v)
  int lca(int u, int v) {
    // go up parent while depth of u and v is same
    if (depth[u] > depth[v])
      std::swap(u, v);
    for (int k = 0; k < log2n; ++k) {
      if ((depth[v] - depth[u]) >> k & 1) {
        v = parent[k][v]; // go up to 2^k if k-th binary is 1
      }
    }

    if (u == v)
      return u; // this case is that v is in u's subtree

    // Find LCA by binary searching
    for (int k = log2n - 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() {
  INIT;
  VAR(int, n);
  std::vector<std::vector<int>> g(n);
  REP(i, n) {
    VAR(int, k);
    VEC(int, c, k);
    REP(j, k) { g[i].emplace_back(c[j]); }
  }
  LCA lca(g, 0);
  VAR(int, Q);
  REP(q, Q) {
    VAR(int, u, v);
    OUT(lca.lca(u, v)) BR;
  }
  return 0;
}