Submission #849231

#	Time	Username	Problem	Language	Result	Execution time	Memory
849231		tch1cherin	Bridges (APIO19_bridges)	C++17	59 / 100	3041 ms	10404 KiB

bridges

#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("avx2")
#include <bits/stdc++.h>
using namespace std;

struct dsu {
  vector<int> parent, rank;
  vector<vector<pair<int*, int>>> changes;

  dsu(int size) : parent(size), rank(size, 1) {
    iota(parent.begin(), parent.end(), 0);
  }

  int get(int u) {
    return parent[u] == u ? u : get(parent[u]);
  }

  void unite(int u, int v) {
    u = get(u), v = get(v);
    changes.push_back({});
    if (u != v) {
      if (rank[u] < rank[v]) {
        swap(u, v);
      }
      changes.back().reserve(2);
      changes.back().push_back({&rank[u], rank[u]});
      changes.back().push_back({&parent[v], parent[v]});
      rank[u] += rank[v];
      parent[v] = u;
    }
  }

  void rollback() {
    for (auto &[x, y] : changes.back()) {
      *x = y; 
    }
    changes.pop_back();
  }
};

struct edge {
  int from, to;
  int weight;
};

bool operator>(edge a, edge b) {
  return a.weight > b.weight;
}

const int BLOCK = 500;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int N, M;
  cin >> N >> M;
  vector<edge> edges(M);
  for (auto &[from, to, weight] : edges) {
    cin >> from >> to >> weight;
    from--, to--;
  }
  int Q;
  cin >> Q;
  vector<int> answer(Q, -1);
  vector<tuple<int, int, int>> changes, queries;
  vector<bool> is_changed(M), used(M);
  for (int i = 0; i < Q; i++) {
    int T;
    cin >> T;
    if (T == 1) {
      int B, R;
      cin >> B >> R;
      B--;
      is_changed[B] = true;
      changes.push_back({i, B, R}); 
    } else {
      int S, W;
      cin >> S >> W;
      S--;
      queries.push_back({i, S, W});
    }
    if ((Q - i - 1) % BLOCK == 0) {
      vector<pair<edge, int>> sorted_edges(M);
      for (int i = 0; i < M; i++) {
        sorted_edges[i] = {edges[i], i};
      }
      sort(sorted_edges.begin(), sorted_edges.end(),
          [](pair<edge, int>& a, pair<edge, int>& b) {
        return a.first > b.first;
      });
      sort(queries.begin(), queries.end(),
          [](tuple<int, int, int> a, tuple<int, int, int> b) {
        return get<2>(a) > get<2>(b);
      });
      int ptr = 0;
      dsu sets(N);
      for (auto [j, S, W] : queries) {
        while (ptr < M && sorted_edges[ptr].first.weight >= W) {
          if (!is_changed[sorted_edges[ptr].second]) {
            sets.unite(sorted_edges[ptr].first.from, sorted_edges[ptr].first.to);
          }
          ptr++;
        }
        int x = (int)changes.size(); 
        for (int k = 0; k < (int)changes.size(); k++) {
          if (get<0>(changes[k]) > j) {
            x = k;
            break;
          }
        }
        int rollbacks = 0;
        for (int k = x - 1; k >= 0; k--) {
          if (!used[get<1>(changes[k])] && get<2>(changes[k]) >= W) {
            auto [from, to, weight] = edges[get<1>(changes[k])];
            sets.unite(from, to);
            rollbacks++;
          }
          used[get<1>(changes[k])] = true;
        }
        for (int k = (int)changes.size() - 1; k >= x; k--) {
          auto [y, B, R] = changes[k];
          if (!used[B] && edges[B].weight >= W) {
            used[B] = true;
            sets.unite(edges[B].from, edges[B].to);
            rollbacks++;
          }
        }
        answer[j] = sets.rank[sets.get(S)];
        for (int k = (int)changes.size() - 1; k >= 0; k--) {
          used[get<1>(changes[k])] = false;
        }
        for (int k = 0; k < rollbacks; k++) {
          sets.rollback();
        }
      }
      for (auto [j, B, R] : changes) {
        is_changed[B] = false;
        edges[B].weight = R;
      }

      vector<tuple<int, int, int>>().swap(changes);
      vector<tuple<int, int, int>>().swap(queries);
    }
  }
  for (int i = 0; i < Q; i++) {
    if (answer[i] != -1) {
      cout << answer[i] << "\n";
    }
  }
}

• Subtask 1: 13 / 13
• Subtask 2: 16 / 16
• Subtask 3: 17 / 17
• Subtask 4: 0 / 14
• Subtask 5: 13 / 13
• Subtask 6: 0 / 27