Problem p02986 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit32(x) (1 << (x))
#define bit64(x) (1ll << (x))

using namespace std;

using i32 = int;
using i64 = long long;
using u64 = unsigned long long;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;
using vu64 = vector<u64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() {
  cout << "Yes" << '\n';
  exit(0);
}
inline void no() {
  cout << "No" << '\n';
  exit(0);
}
inline i64 gcd(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  if (a % b == 0)
    return b;
  return gcd(b, a % b);
}
inline i64 lcm(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  return a / gcd(a, b) * b;
}
inline u64 xorshift() {
  static u64 x = 88172645463325252ull;
  x = x ^ (x << 7);
  return x = x ^ (x >> 9);
}
template <typename T>
class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T>
class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> inline void amax(T &x, T y) {
  if (x < y)
    x = y;
}
template <typename T> inline void amin(T &x, T y) {
  if (x > y)
    x = y;
}
template <typename T> inline T exp(T x, i64 n, T e = 1) {
  T r = e;
  while (n > 0) {
    if (n & 1)
      r *= x;
    x *= x;
    n >>= 1;
  }
  return r;
}
template <typename T> inline T bis(T ok, T ng, function<bool(T)> f, T eps = 1) {
  while (abs(ok - ng) > eps) {
    T mi = (ok + ng) / 2;
    (f(mi) ? ok : ng) = mi;
  }
  return ok;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  each(x, v) is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  rep(i, v.size()) {
    if (i)
      os << ' ';
    os << v[i];
  }
  return os;
}
void solve();
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout << fixed << setprecision(16);
  solve();
  return 0;
}

template <typename T> struct WeightedGraph {
  struct Edge {
    int to;
    T cost;
    int col;
  };
  vector<vector<Edge>> edges;
  int n;
  WeightedGraph(int n) : n(n) { edges = vector<vector<Edge>>(n); }
  void add_edge(int from, int to, T cost, int col) {
    edges[from].push_back((Edge){to, cost, col});
  }
  vector<Edge> &operator[](int x) { return edges[x]; }
};

struct LCA {
  WeightedGraph<int> g;
  vector<vi32> par;
  vi32 dep;
  LCA(WeightedGraph<int> &g) : g(g), par(30, vi32(g.n + 1, g.n)), dep(g.n) {
    dfs(0, -1, 0);
    rep(i, 29) rep(j, g.n) { par[i + 1][j] = par[i][par[i][j]]; }
  }
  void dfs(int u, int p, int d) {
    dep[u] = d;
    each(e, g[u]) if (e.to != p) {
      par[0][e.to] = u;
      dfs(e.to, u, d + 1);
    }
  }
  int operator()(int u, int v) {
    if (dep[u] < dep[v])
      swap(u, v);
    rep(i, 30) {
      if ((dep[u] - dep[v]) & bit32(i))
        u = par[i][u];
    }
    if (u == v)
      return u;
    rrep(i, 30) {
      if (par[i][u] != par[i][v]) {
        u = par[i][u];
        v = par[i][v];
      }
    }
    return par[0][u];
  }
};

void solve() {
  int N, Q;
  cin >> N >> Q;
  WeightedGraph<int> g(N);
  rep(i, N - 1) {
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    a--, b--;
    g.add_edge(a, b, d, c);
    g.add_edge(b, a, d, c);
  }

  auto lca = LCA(g);

  struct Query {
    int a, c, d, i;
  };

  i64 sum = 0;
  vi64 col_sum(N);
  vi64 col_cnt(N);
  vi64 ans(N);
  vector<vector<Query>> query(N);

  rep(i, Q) {
    int x, y, u, v;
    cin >> x >> y >> u >> v;
    u--, v--;
    int p = lca(u, v);
    query[u].push_back((Query){i, x, y, 1});
    query[v].push_back((Query){i, x, y, 1});
    query[p].push_back((Query){i, x, y, -2});
  }

  auto dfs = [&](auto dfs, int u, int p) -> void {
    each(q, query[u]) {
      i64 x = sum - col_sum[q.c];
      x += col_cnt[q.c] * q.d;
      ans[q.a] += x * q.i;
    }
    each(e, g[u]) if (e.to != p) {
      sum += e.cost;
      col_sum[e.col] += e.cost;
      col_cnt[e.col] += 1;
      dfs(dfs, e.to, u);
      sum -= e.cost;
      col_sum[e.col] -= e.cost;
      col_cnt[e.col] -= 1;
    }
  };
  dfs(dfs, 0, -1);

  rep(i, Q) cout << ans[i] << endl;
}


Fixed submission:
#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit32(x) (1 << (x))
#define bit64(x) (1ll << (x))

using namespace std;

using i32 = int;
using i64 = long long;
using u64 = unsigned long long;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;
using vu64 = vector<u64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() {
  cout << "Yes" << '\n';
  exit(0);
}
inline void no() {
  cout << "No" << '\n';
  exit(0);
}
inline i64 gcd(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  if (a % b == 0)
    return b;
  return gcd(b, a % b);
}
inline i64 lcm(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  return a / gcd(a, b) * b;
}
inline u64 xorshift() {
  static u64 x = 88172645463325252ull;
  x = x ^ (x << 7);
  return x = x ^ (x >> 9);
}
template <typename T>
class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T>
class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> inline void amax(T &x, T y) {
  if (x < y)
    x = y;
}
template <typename T> inline void amin(T &x, T y) {
  if (x > y)
    x = y;
}
template <typename T> inline T exp(T x, i64 n, T e = 1) {
  T r = e;
  while (n > 0) {
    if (n & 1)
      r *= x;
    x *= x;
    n >>= 1;
  }
  return r;
}
template <typename T> inline T bis(T ok, T ng, function<bool(T)> f, T eps = 1) {
  while (abs(ok - ng) > eps) {
    T mi = (ok + ng) / 2;
    (f(mi) ? ok : ng) = mi;
  }
  return ok;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  each(x, v) is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  rep(i, v.size()) {
    if (i)
      os << ' ';
    os << v[i];
  }
  return os;
}
void solve();
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout << fixed << setprecision(16);
  solve();
  return 0;
}

template <typename T> struct WeightedGraph {
  struct Edge {
    int to;
    T cost;
    int col;
  };
  vector<vector<Edge>> edges;
  int n;
  WeightedGraph(int n) : n(n) { edges = vector<vector<Edge>>(n); }
  void add_edge(int from, int to, T cost, int col) {
    edges[from].push_back((Edge){to, cost, col});
  }
  vector<Edge> &operator[](int x) { return edges[x]; }
};

struct LCA {
  WeightedGraph<int> g;
  vector<vi32> par;
  vi32 dep;
  LCA(WeightedGraph<int> &g) : g(g), par(30, vi32(g.n + 1, g.n)), dep(g.n) {
    dfs(0, -1, 0);
    rep(i, 29) rep(j, g.n) { par[i + 1][j] = par[i][par[i][j]]; }
  }
  void dfs(int u, int p, int d) {
    dep[u] = d;
    each(e, g[u]) if (e.to != p) {
      par[0][e.to] = u;
      dfs(e.to, u, d + 1);
    }
  }
  int operator()(int u, int v) {
    if (dep[u] < dep[v])
      swap(u, v);
    rep(i, 30) {
      if ((dep[u] - dep[v]) & bit32(i))
        u = par[i][u];
    }
    if (u == v)
      return u;
    rrep(i, 30) {
      if (par[i][u] != par[i][v]) {
        u = par[i][u];
        v = par[i][v];
      }
    }
    return par[0][u];
  }
};

void solve() {
  int N, Q;
  cin >> N >> Q;
  WeightedGraph<int> g(N);
  rep(i, N - 1) {
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    a--, b--;
    g.add_edge(a, b, d, c);
    g.add_edge(b, a, d, c);
  }

  auto lca = LCA(g);

  struct Query {
    int a, c, d, i;
  };

  i64 sum = 0;
  vi64 col_sum(N);
  vi64 col_cnt(N);
  vi64 ans(Q);
  vector<vector<Query>> query(N);

  rep(i, Q) {
    int x, y, u, v;
    cin >> x >> y >> u >> v;
    u--, v--;
    int p = lca(u, v);
    query[u].push_back((Query){i, x, y, 1});
    query[v].push_back((Query){i, x, y, 1});
    query[p].push_back((Query){i, x, y, -2});
  }

  auto dfs = [&](auto dfs, int u, int p) -> void {
    each(q, query[u]) {
      i64 x = sum - col_sum[q.c];
      x += col_cnt[q.c] * q.d;
      ans[q.a] += x * q.i;
    }
    each(e, g[u]) if (e.to != p) {
      sum += e.cost;
      col_sum[e.col] += e.cost;
      col_cnt[e.col] += 1;
      dfs(dfs, e.to, u);
      sum -= e.cost;
      col_sum[e.col] -= e.cost;
      col_cnt[e.col] -= 1;
    }
  };
  dfs(dfs, 0, -1);

  rep(i, Q) cout << ans[i] << endl;
}