Submission #1140181

#	Time	Username	Problem	Language	Result	Execution time	Memory
1140181		argon1	Monthly railway pass (LMIO18_menesinis_bilietas)	C++20	0 / 100	3090 ms	176752 KiB

menesinis_bilietas

#include <iostream>
#include <vector>
#include <unordered_map>
#include <unordered_set>
#include <queue>
using namespace std;

const int MAXN = 500000;

vector<int> trainGraph[MAXN + 1];
vector<int> busGraph[MAXN + 1];
vector<int> trainComponent(MAXN + 1, -1);
unordered_map<int, unordered_set<int>> componentCities; // Cities in each train component
unordered_map<int, unordered_set<int>> componentNeighbors; // Components reachable via one bus

// Perform BFS to find all cities in the same train component
void bfsTrain(int start, int componentID) {
    queue<int> q;
    q.push(start);
    trainComponent[start] = componentID;
    componentCities[componentID].insert(start);

    while (!q.empty()) {
        int city = q.front();
        q.pop();
        for (int neighbor : trainGraph[city]) {
            if (trainComponent[neighbor] == -1) {
                trainComponent[neighbor] = componentID;
                componentCities[componentID].insert(neighbor);
                q.push(neighbor);
            }
        }
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, M;
    cin >> N >> M;

    // Build the graph
    for (int i = 0; i < M; ++i) {
        int a, b;
        char type;
        cin >> a >> b >> type;
        if (type == 'T') {
            trainGraph[a].push_back(b);
            trainGraph[b].push_back(a);
        } else if (type == 'A') {
            busGraph[a].push_back(b);
            busGraph[b].push_back(a);
        }
    }

    // Step 1: Find train components
    int componentCount = 0;
    for (int i = 1; i <= N; ++i) {
        if (trainComponent[i] == -1) {
            bfsTrain(i, componentCount++);
        }
    }

    // Step 2: Precompute neighbors of each train component via one bus trip
    for (int city = 1; city <= N; ++city) {
        int currentComponent = trainComponent[city];
        for (int neighbor : busGraph[city]) {
            int neighborComponent = trainComponent[neighbor];
            if (currentComponent != neighborComponent) {
                componentNeighbors[currentComponent].insert(neighborComponent);
            }
        }
    }

    // Step 3: Calculate the maximum reachable cities for each city
    int maxReachable = 0, countMaxCities = 0;

    for (int city = 1; city <= N; ++city) {
        int currentComponent = trainComponent[city];

        // Start with all cities in the current train component
        unordered_set<int> reachableCities = componentCities[currentComponent];

        // Add cities from other components reachable via a single bus trip
        for (int neighborComponent : componentNeighbors[currentComponent]) {
            reachableCities.insert(componentCities[neighborComponent].begin(),
                                   componentCities[neighborComponent].end());
        }

        int reachableCount = reachableCities.size();
        if (reachableCount > maxReachable) {
            maxReachable = reachableCount;
            countMaxCities = 1;
        } else if (reachableCount == maxReachable) {
            countMaxCities++;
        }
    }

    // Step 4: Output the result
    cout << countMaxCities << "\n";
    return 0;
}

• Subtask 1: 0 / 10
• Subtask 2: 0 / 6
• Subtask 3: 0 / 30
• Subtask 4: 0 / 35
• Subtask 5: 0 / 19