#include <bits/stdc++.h>

using namespace std;

vector<int> bfs(const vector<vector<int>> &adjacency, int start) {
    int n = static_cast<int>(adjacency.size()); // Number of vertices (assumes vertices are 0‑based)

    vector<bool> visited(n, false); // Tracks whether a vertex has been discovered
    queue<int> q; // FIFO container for the frontier

    // Initialise the search
    visited[start] = true;
    q.push(start);

    while (!q.empty()) {
        int u = q.front(); q.pop(); // Dequeue the next vertex

        // Explore all neighbours of u
        for (int v : adjacency[u]) {
            if (!visited[v]) { // If neighbour not seen before
                visited[v] = true; // Mark as discovered
                q.push(v); // Enqueue for later processing
            }
        }
    }
}