BFS-distances

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

ifstream f("bfs.in");
ofstream g("bfs.out");

const int NMAX = 100005;
int N, M, S, dist[NMAX];
vector < int > Muchii[NMAX];
queue < int > Q;

void BFS()
{
    int nod,vecin;
    while(!Q.empty())
    {
        nod=Q.front();
        Q.pop();
        for(unsigned int i=0;i<Muchii[nod].size();i++)
        {
            vecin=Muchii[nod][i];
            if(dist[vecin]==-1)
            {
                Q.push(vecin);
                dist[vecin]=dist[nod]+1;
            }
        }
    }
}

void Citire()
{
    f>>N>>M>>S;
    for(int i=1;i<=M;i++)
    {
        int x,y;
        f>>x>>y;
        Muchii[x].push_back(y);
    }
}

int main()
{
    Citire();
    for(int i=1;i<=N;i++) dist[i]=-1;
    dist[S]=0;
    Q.push(S);
    BFS();
    for(int i=1;i<=N;i++) g<<dist[i]<<" ";
    f.close();
    g.close();
    return 0;
}