Distinct Routes

#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;

const int MAXN = 501;
vector<int> adj[MAXN];
vector<int> parent(MAXN, -1);

// Function to find the shortest path using BFS
bool bfs(int n) {
    queue<int> q;
    vector<bool> visited(n + 1, false);
    parent.assign(n + 1, -1);  // Reset parent array
    visited[1] = true;
    q.push(1);

    while (!q.empty()) {
        int u = q.front();
        q.pop();

        if (u == n) {
            return true;  // We have reached room `n`
        }

        for (int v : adj[u]) {
            if (!visited[v]) {
                visited[v] = true;
                parent[v] = u;
                q.push(v);
            }
        }
    }

    return false;  // No more paths can be found
}

// Function to remove the used path from the graph
void remove_path(int n) {
    int u = n;
    while (parent[u] != -1) {
        int p = parent[u];
        adj[p].erase(remove(adj[p].begin(), adj[p].end(), u), adj[p].end());
        u = p;
    }
}

int main() {
    int n, m;
    cin >> n >> m;

    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        adj[a].push_back(b);
    }

    vector<vector<int>> routes;

    // Keep finding paths and removing them
    while (bfs(n)) {
        vector<int> path;
        int u = n;
        while (u != -1) {
            path.push_back(u);
            u = parent[u];
        }
        reverse(path.begin(), path.end());  // Path from room 1 to n
        routes.push_back(path);
        remove_path(n);  // Remove the used path from the graph
    }

    // Output the number of routes (days) and each route
    cout << routes.size() << endl;
    for (const auto& route : routes) {
        cout << route.size() << endl;
        for (int room : route) {
            cout << room << " ";
        }
        cout << endl;
    }

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: WRONG ANSWER