Submission #385580

#	Time	Username	Problem	Language	Result	Execution time	Memory
385580		ntabc05101	Bridges (APIO19_bridges)	C++14	100 / 100	2519 ms	32372 KiB

bridges

#include<bits/stdc++.h>
using namespace std;

const int block = 1000;
const int mx = 100000;

int parent[5 + mx], sz[5 + mx];
stack<int> st;

void init(int n) {
        iota(parent, parent + n, 0);
        fill(sz, sz + n, 1);
}

int find(int x) {
        while (x != parent[x]) {
                x = parent[x];
        }
        return x;
}

void unite_set(int x, int y) {
        x = find(x), y = find(y);
        if (x == y) {
                return ;
        }

        if (sz[x] < sz[y]) {
                swap(x, y);
        }
        st.emplace(y);
        parent[y] = x;
        sz[x] += sz[y];
}

void roll_back(int x) {
        while (st.size() > x) {
                int y = st.top();
                st.pop();

                sz[parent[y]] -= sz[y];
                parent[y] = y;
        }
}

int n, m, q;
int u[5 + mx], v[5 + mx], w[5 + mx];
int t[5 + mx], x[5 + mx], y[5 + mx];
bool changed[5 + mx];
vector<int> to_join[block];
int result[5 + mx];

int main() {
        ios_base::sync_with_stdio(0); cin.tie(0);

        cin >> n >> m;
        for (int i = 0; i < m; i++) {
                cin >> u[i] >> v[i] >> w[i];
                u[i]--, v[i]--;
        }
        cin >> q;
        for (int i = 0; i < q; i++) {
                cin >> t[i] >> x[i] >> y[i];
                x[i]--;
        }

        fill(changed, changed + m, false);
        for (int l = 0; l < q; l += block) {
                int r = min(l + block, q);
                init(n);

                vector<int> ask, upd, unchanged;
                for (int i = l; i < r; i++) {
                        if (t[i] == 1) {
                                changed[x[i]] = true;
                                upd.emplace_back(i);
                        }
                        else {
                                ask.emplace_back(i);
                        }
                }

                for (int i = 0; i < m; i++) {
                        if (!changed[i]) {
                                unchanged.emplace_back(i);
                        }
                        else {
                                changed[i] = false;
                        }
                }

                for (int i = l; i < r; i++) {
                        if (t[i] == 1) {
                                w[x[i]] = y[i];
                        }
                        else {
                                to_join[i - l].clear();
                                for (auto& u: upd) {
                                        if (w[x[u]] >= y[i]) {
                                                to_join[i - l].emplace_back(x[u]);
                                        }
                                }
                        }
                }

                sort(begin(ask), end(ask), [&](int const& a, int const& b) {
                        return y[a] > y[b];
                });
                sort(begin(unchanged), end(unchanged), [&](int const& a, int const& b) {
                        return w[a] > w[b];
                });

                int p = 0;
                for (int& i: ask) {
                        while (p < unchanged.size() && w[unchanged[p]] >= y[i]) {
                                unite_set(u[unchanged[p]], v[unchanged[p]]);
                                p++;
                        }

                        int pre_sz = st.size();
                        for (int& j: to_join[i - l]) {
                                unite_set(u[j], v[j]);
                        }
                        result[i] = sz[find(x[i])];

                        roll_back(pre_sz);
                }
        }

        for (int i = 0; i < q; i++) {
                if (t[i] == 2) {
                        cout << result[i] << "\n";
                }
        }

        return 0;
}

Compilation message (stderr)

bridges.cpp: In function 'void roll_back(int)':
bridges.cpp:37:26: warning: comparison of integer expressions of different signedness: 'std::stack<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   37 |         while (st.size() > x) {
      |                ~~~~~~~~~~^~~
bridges.cpp: In function 'int main()':
bridges.cpp:115:34: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  115 |                         while (p < unchanged.size() && w[unchanged[p]] >= y[i]) {
      |                                ~~^~~~~~~~~~~~~~~~~~

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