graph breadth walk

#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <list>

using namespace std;
typedef vector<vector<int>> GraphType;

list<size_t> get_neighbours(const GraphType& graph, const vector<bool>& visits, size_t target)
{
    list<size_t> result;

    for (size_t i = 0; i < graph.size(); ++i)
    {
        if (0 != graph[target][i] && !visits[i])
            result.push_back(i);
    }

    return result;
}

void walk_some_vertice(const GraphType& graph, vector<bool>& visits, size_t target)
{
    visits[target] = true;
    cout << "We are at node: " << target << endl;

    list<size_t> neighbours = get_neighbours(graph, visits, target);
    while(!neighbours.empty())
    {
        size_t new_target = neighbours.front();
        visits[new_target] = true;
        cout << "We are at node: " << new_target << endl;

        neighbours.splice(end(neighbours), get_neighbours(graph, visits, new_target));
        neighbours.pop_front();
    }
}

void breadth_walk(const GraphType& graph)
{
    vector<bool> visited(graph.size(), false);

    for(size_t i = 0; i < graph.size(); ++i)
    {
        if (!visited[i])
            walk_some_vertice(graph, visited, i);
    }
}

int main()
{
    GraphType graph;

    unsigned N;
    cin >> N;

    graph.resize(N, vector<int>(N, 0));

    string line;
    getline(cin, line);

    for (unsigned i = 0; i < N; ++i)
    {
        getline(cin, line);
        stringstream x(line);

        size_t neighbour;
        while (x >> neighbour)
        {
            graph[i][neighbour] = 1;
            graph[neighbour][i] = 1;
        }

        graph[i][i] = 0;
    }

    for(auto line : graph)
    {
        for(int val: line)
            cout << val << '\t';
        cout << endl;
    }

    breadth_walk(graph);

    return 0;
}