Submission #556920

#	Time	Username	Problem	Language	Result	Execution time	Memory
556920		Jomnoi	Bridges (APIO19_bridges)	C++17	27 / 100	1607 ms	524288 KiB

bridges

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

const int MAX_N = 5e4 + 10;
const int MAX_M = 1e5 + 10;
const int MAX_Q = 1e5 + 10;

int parent[MAX_N], sz[MAX_N];
int U[MAX_M], V[MAX_M], D[MAX_M];
int T[MAX_Q], X[MAX_Q], Y[MAX_Q];
bool changed[MAX_M];
int ans[MAX_Q];
vector <int> unchanged, update, query, tojoin[MAX_Q];
stack <int> stk;

int root(int u) {
    if(u == parent[u]) {
        return u;
    }
    return root(parent[u]);
}

void merge(int u, int v) {
    u = root(u), v = root(v);
    if(u == v) {
        return;
    }

    if(sz[u] < sz[v]) {
        swap(u, v);
    }
    sz[u] += sz[v];
    parent[v] = u;
    stk.push(v);
}

void rollback(int timer) {
    while(stk.size() > timer) {
        int v = stk.top();
        stk.pop();

        sz[root(v)] -= sz[v];
        parent[v] = v;
    }
}

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int N, M;
    cin >> N >> M;

    iota(parent + 1, parent + N + 1, 1);
    fill(sz + 1, sz + N + 1, 1);

    for(int i = 1; i <= M; i++) {
        cin >> U[i] >> V[i] >> D[i];
    }

    int Q;
    cin >> Q;
    for(int i = 1; i <= Q; i++) {
        cin >> T[i] >> X[i] >> Y[i];
        if(T[i] == 1) {
            changed[X[i]] = true;
            update.push_back(i);
        }
        else {
            query.push_back(i);
        }
    }

    for(int i = 1; i <= M; i++) {
        if(changed[i] == false) {
            unchanged.push_back(i);
        }
    }

    for(int i = 1; i <= Q; i++) {
        if(T[i] == 1) {
            D[X[i]] = Y[i];
        }
        else {
            for(auto u : update) {
                if(D[X[u]] >= Y[i]) {
                    tojoin[i].push_back(X[u]);
                }
            }
        }
    }

    sort(query.begin(), query.end(), [&](const int &a, const int &b) {
        return Y[a] > Y[b];
    });
    sort(unchanged.begin(), unchanged.end(), [&](const int &a, const int &b) {
        return D[a] > D[b];
    });

    int j = 0;
    for(auto i : query) {
        while(j < unchanged.size() and D[unchanged[j]] >= Y[i]) {
            merge(U[unchanged[j]], V[unchanged[j]]);
            j++;
        }

        int timer = stk.size();
        for(auto e : tojoin[i]) {
            merge(U[e], V[e]);
        }

        ans[i] = sz[root(X[i])];
        
        rollback(timer);
    }

    for(int i = 1; i <= Q; i++) {
        if(T[i] == 2) {
            cout << ans[i] << '\n';
        }
    }
    return 0;
}

Compilation message (stderr)

bridges.cpp: In function 'void rollback(int)':
bridges.cpp:39:22: warning: comparison of integer expressions of different signedness: 'std::stack<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   39 |     while(stk.size() > timer) {
      |           ~~~~~~~~~~~^~~~~~~
bridges.cpp: In function 'int main()':
bridges.cpp:101:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  101 |         while(j < unchanged.size() and D[unchanged[j]] >= Y[i]) {
      |               ~~^~~~~~~~~~~~~~~~~~

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