Problem p02648 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint inf = 1LL << 60;
const lint mod = 1000000007;

template <class T> bool chmax(T &a, const T &b) {
  return (a < b) ? (a = b, 1) : 0;
}
template <class T> bool chmin(T &a, const T &b) {
  return (b < a) ? (a = b, 1) : 0;
}

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  lint n;
  cin >> n;
  vector<lint> V(n + 1), W(n + 1);
  for (int i = 1; i < n + 1; ++i) {
    cin >> V[i] >> W[i];
  }
  lint q;
  cin >> q;
  vector<lint> v(q + 1), l(q + 1);
  vector<bool> calc(1000000, false);
  lint up = 1 << 10;
  vector<vector<pair<int, pair<int, int>>>> qs(1000000);
  for (int i = 0; i < q; ++i) {
    cin >> v[i] >> l[i];
    int c = v[i];
    // ls[c]      = {i, l[i]};
    bool added = false;
    if (c < (up)) {
      qs[c].push_back({i, {v[i], l[i]}});
      added = true;
    }
    while (c != 0) {
      if (!added && (c < (up))) {
        qs[c].push_back({i, {v[i], l[i]}});
        added = true;
      }
      if (c < (up)) {
        calc[c] = true;
      }
      c /= 2;
    }
  }
  // 1 - indexed!!!!!!

  vector<lint> ret(q, 0);
  function<void(int, map<lint, lint> &)> dfs = [&](int c, map<lint, lint> &dp) {
    map<lint, lint> to;
    to[0] = 0;
    for (auto &d : dp) {
      chmax(to[d.first], d.second);
      if (d.first + W[c] <= 100000)
        chmax(to[d.first + W[c]], d.second + V[c]);
    }
    if (qs[c].size() != 0) {
      lint mx = 0;
      map<lint, lint> tod = to;
      tod[0] = 0;
      for (auto it = tod.begin(); it != tod.end(); it = next(it)) {
        chmax(it->second, mx);
        chmax(mx, it->second);
      }
      for (auto &p : qs[c]) {
        vector<lint> vv = {0}, ww = {0};
        lint curr = p.second.first;
        while (curr > c) {
          vv.push_back(V[curr]);
          ww.push_back(W[curr]);
          curr /= 2;
        }
        int k = vv.size();
        lint r = 0;
        for (int j = 0; j < 1 << k; ++j) {
          lint vs = 0;
          lint ws = 0;
          for (int x = 0; x < k; ++x) {
            if (j >> x & 1) {
              vs += vv[x];
              ws += ww[x];
            }
          }
          if (ws <= p.second.second) {
            auto it = tod.upper_bound(p.second.second - ws);
            if (it == tod.begin())
              continue;
            lint mx = prev(it)->second;
            chmax(r, vs + mx);
          }
        }
        ret[p.first] = r;
      }
    }

    for (auto &v : {c * 2, c * 2 + 1}) {
      if ((v > n) || (v >= (up)) || !calc[v]) {
        continue;
      }
      dfs(v, to);
    }
  };
  map<lint, lint> vv;
  vv[0] = 0;
  dfs(1, vv);

  for (int i = 0; i < q; ++i) {
    cout << ret[i] << "\n";
  }
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint inf = 1LL << 60;
const lint mod = 1000000007;

template <class T> bool chmax(T &a, const T &b) {
  return (a < b) ? (a = b, 1) : 0;
}
template <class T> bool chmin(T &a, const T &b) {
  return (b < a) ? (a = b, 1) : 0;
}

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  lint n;
  cin >> n;
  vector<lint> V(n + 1), W(n + 1);
  for (int i = 1; i < n + 1; ++i) {
    cin >> V[i] >> W[i];
  }
  lint q;
  cin >> q;
  vector<lint> v(q + 1), l(q + 1);
  vector<bool> calc(1000000, false);
  lint up = 1 << 10;
  vector<vector<pair<int, pair<int, int>>>> qs(1000000);
  for (int i = 0; i < q; ++i) {
    cin >> v[i] >> l[i];
    int c = v[i];
    // ls[c]      = {i, l[i]};
    bool added = false;
    if (c < (up)) {
      qs[c].push_back({i, {v[i], l[i]}});
      added = true;
    }
    while (c != 0) {
      if (!added && (c < (up))) {
        qs[c].push_back({i, {v[i], l[i]}});
        added = true;
      }
      if (c < (up)) {
        calc[c] = true;
      }
      c /= 2;
    }
  }
  // 1 - indexed!!!!!!

  vector<lint> ret(q, 0);
  function<void(int, map<lint, lint> &)> dfs = [&](int c, map<lint, lint> &dp) {
    map<lint, lint> to;
    to[0] = 0;
    for (auto &d : dp) {
      chmax(to[d.first], d.second);
      if (d.first + W[c] <= 100000)
        chmax(to[d.first + W[c]], d.second + V[c]);
    }
    if (qs[c].size() != 0) {
      lint mx = 0;
      map<lint, lint> tod = to;
      tod[0] = 0;
      for (auto it = tod.begin(); it != tod.end(); it = next(it)) {
        chmax(it->second, mx);
        chmax(mx, it->second);
      }
      for (auto &p : qs[c]) {
        vector<lint> vv, ww;
        lint curr = p.second.first;
        while (curr > c) {
          vv.push_back(V[curr]);
          ww.push_back(W[curr]);
          curr /= 2;
        }
        int k = vv.size();
        lint r = 0;
        for (int j = 0; j < 1 << k; ++j) {
          lint vs = 0;
          lint ws = 0;
          for (int x = 0; x < k; ++x) {
            if (j >> x & 1) {
              vs += vv[x];
              ws += ww[x];
            }
          }
          if (ws <= p.second.second) {
            auto it = tod.upper_bound(p.second.second - ws);
            if (it == tod.begin())
              continue;
            lint mx = prev(it)->second;
            chmax(r, vs + mx);
          }
        }
        ret[p.first] = r;
      }
    }

    for (auto &v : {c * 2, c * 2 + 1}) {
      if ((v > n) || (v >= (up)) || !calc[v]) {
        continue;
      }
      dfs(v, to);
    }
  };
  map<lint, lint> vv;
  vv[0] = 0;
  dfs(1, vv);

  for (int i = 0; i < q; ++i) {
    cout << ret[i] << "\n";
  }
  return 0;
}