Error: infinite loop in my code(Depth First Search)

I code the algorithm Depth First Search, but it infinite loop, what did i wrong?

Code:

---

#include <iostream>
#include <vector>
using std::cout;
using std::cin;
using std::endl;
const int maxx = 20;
void Read_input_from_user(bool grid[][maxx], int vertices)
{
    int u, v;
    for(int x = 0; x < vertices; ++x)
    {
        cout << "Enter u : \t";
        cin >> u;
        u--;
        cout << "Enter v : \t";
        cin >> v;
        v--;
        grid[u][v] = true;
        grid[v][u] = true;
        cout << "---------------------\n";
    }
}

void Depth_first_search(bool grid[][maxx], std::vector<int> &trace,
                        int nodes, int u)
{
       
       
    for(int v = 0; v < nodes; ++v)
    {
        if((grid[u][v] == true) && trace[v] == 0)
        {
                       
            trace[v] = u;
                       
            //recursive step
            Depth_first_search(grid, trace, nodes, v);
                       
        }
    }
}

void Trace_result(std::vector<int> &trace, int start, int end, int nodes)
{ 
    cout << "From _nodes" << start + 1 << " you can visit :\n";
    for(int v = 0; v < nodes; ++v)
    {
        if(trace[v] != 0)
        {
            cout << " _nodes : " << v + 1 << " , ";
        }
    }

    cout << "\n--------------------------------------------\n";
    cout << "The path from " << start + 1 << " to " << end + 1 << '\n';
   
    if(trace[end] == 0){
        cout << "Unavailable.! to go to from " << end + 1
            << " to -> " << start + 1 << '\n';
    }
    else{
        while(end != start)
        {
            cout << end + 1 << "<-";
            end = trace[end];
        }
        cout << start + 1 << endl;
    }
}

int main()
{
    bool grid[maxx][maxx] = { false };
    std::vector<int> trace(maxx, 0);
    int nodes, vertices;
    cout << "Please input the number of Node : \n";
    cin >> nodes;
    cout << "Please input the number of Vertices : \n";
    cin >> vertices;

    //Set value for all vertices.
    Read_input_from_user(grid, vertices);

    //Read the necessary path
    int starting_position, finishing_position;
    cout << "Please Input the Starting Node : \n";
    cin >> starting_position;
    cout << "Please Input the Finishing Node : \n";
    cin >> finishing_position;
    //Decrease to fit with index of C++ start from 0->size-1
    starting_position--;
    finishing_position--;

    Depth_first_search(grid, trace, nodes, starting_position);
    Trace_result(trace, starting_position, finishing_position, nodes);
        system("pause");
    return 0;
}

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I'm wrong in: Depth_first_search, is't it?

Have you tried stepping through your code in the debugger?

>"< i don't know how to use degger in C#, i'm begginer

This is a C++ forum, not C#. You need to learn to use the debugger. It's not optional, and it's the first thing any of us here would do to figure out what was wrong with your code.