Calculates a bfs-order of a graph

bfs.cpp

#include <iostream>
#include <vector>
#include <queue>

using namespace std;

/*
 * This program reads a simple undireced graph from stdin and preforms
 * a BFS on the given graph. The format is as follows:
 * n m
 * e1 e2
 * ...
 *
 * The first line contains the number of vertices and edges of
 * the graph. The following m lines contain one edge each.
 * An edge is represented by two distinct integers between 0 and n-1,
 * being the two respective endpoints of the edge.
 *
 * */

void bfs(vector<vector<int> > & g, vector<int> & order){
  int n = (int)g.size();
  vector<bool> seen(n,false);
  queue<int> q;
  seen[0] = true;
  q.push(0);
  while(!q.empty()){
    int x = q.front();
    order.push_back(x);
    q.pop();
    for(auto y : g[x]){
      if(!seen[y]){
        q.push(y);
        seen[y] = true;
      }
    }
  }
}

int main(){

  //setting up the graph
  int n,m;
  cin >> n >> m;
  vector<vector<int> > g(n,vector<int> ());
  vector<int> order;
  while(m--){
    int a,b;
    cin >> a >> b;
    g[a].push_back(b);
    g[b].push_back(a);
  }

  //bfs call
  bfs(g,order);

  //printing the order
  cout << "One BFS order of the graph is:" << endl;
  for(auto x: order){
    cout << x << " ";
  }
  cout << endl;

  return 0;
}