BFS

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

struct node{
    vector <int> polaczenia;
    int self = 10000000;
};

node graph[1000000];

void BFS(int START = 1, int value = -1)
{
    graph[START].self = value + 1;
    int ile;
    for(int i = 0; i < graph[START].polaczenia.size(); i++){
        ile = graph[START].polaczenia[i];
        if(graph[START].self + 1 < graph[ile].self){
            BFS(ile,graph[START].self);
        }
    }
}

int main()
{
    int n,m,from, to, cost;
    cin >> n >> m;

    for(int i = 0;i < m; i++)
    {
        cin >> from >> to;
        graph[from].polaczenia.push_back(to);
        graph[to].polaczenia.push_back(from);
    }

    BFS();

    for(int i = 1; i <= n; i++)
        if(graph[i].self != 10000000)
            cout << graph[i].self << endl;
        else
            cout << -1 << endl;
}