граф работает

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

const int p = 2000000033;
const int c = 3;

struct vertex
{
    bool visited = false;
    vector<struct adj_vertex> adj_list;
    int list_size = 0;
    int label = -1;
};

struct adj_vertex
{
    int idx;
    int edge_value;
};

class Graph
{
    vertex* G;
    int size;

public:
    Graph(int n);
    int get_size();
    void addEdge(int i, int j, int key);
    void print_graph();
    void DFS(int v_idx, int value, bool& flag);
    bool is_correct();
};

Graph::Graph(int n)
{
    G = new vertex[n];
    size = n;
}

int Graph::get_size()
{
    return this->size;
}

void Graph::addEdge(int i, int j, int key)
{

    adj_vertex tmp;
    tmp.idx = j;
    tmp.edge_value = key;

    G[i].adj_list.push_back(tmp);

    tmp.idx = i;
    G[j].adj_list.push_back(tmp);

    G[i].list_size++;
    G[j].list_size++;
}


void Graph::print_graph()
{
    cout << "\n print:" << endl;
    for (int i = 0; i < size; i++)
    {
        cout << "visited = " << G[i].visited << "; i= " << i << "; ";
        cout << " label = " << G[i].label << " : ";
        int size = G[i].adj_list.size();

        cout << "idx =: ";
        for (int j = 0; j < size; ++j)
        {
            cout << G[i].adj_list[j].idx << " ";
        }


        cout << ";   edge_value =: ";
        for (int j = 0; j < size; ++j)
        {
            cout << G[i].adj_list[j].edge_value << " ";
        }
        cout << endl;
    }
}

void Graph::DFS(int v_idx, int value, bool& flag) //мб лучше не по указателю по индексу
{

    if (flag)
    {
        G[v_idx].visited = true;
        G[v_idx].label = value;

        vertex u;
        vector<struct adj_vertex> curr_list = G[v_idx].adj_list;
        int u_idx, val, edge_value;

        for (int i = 0; i < G[v_idx].list_size; ++i)
        {

            u_idx = curr_list[i].idx;
            u = G[u_idx];
            edge_value = curr_list[i].edge_value;

            if (!(u.visited))
            {
                val = edge_value - value;
                DFS(u_idx, val, flag);
            }

            if (G[u_idx].label + G[v_idx].label != edge_value)
            {
                flag = false;
            }
        }
    }
}


bool Graph::is_correct()
{

    bool flag = true;
    for (int i = 0; i < this->size; ++i)
    {
        if (!G[i].visited)
            DFS(i, 0, flag);
        if (!flag)
            return false;
    }
    return true;
}

int main()
{

    Graph g(12);

    g.addEdge(0, 1, 5);
    g.addEdge(1, 2, 4);
    g.addEdge(3, 4, 3);
    g.addEdge(5, 6, 5);
    g.addEdge(6, 7, 6);
    g.addEdge(7, 8, 7);
    g.addEdge(7, 11, 3);
    g.addEdge(7, 9, 2);
    g.addEdge(9, 10, 1);

    cout << g.is_correct() << endl;

    // g.print_graph();

    return 0;
}