---

using System;
using System.Windows.Forms;

namespace GraphMatrixApp
{
    public partial class Form1 : Form
    {
        int[,] matrix;

        public Form1()
        {
            InitializeComponent();
        }

        private void btnCreate_Click(object sender, EventArgs e)
        {
            int n = (int)numericUpDown1.Value;

            if (n <= 0)
            {
                listBox2.Items.Add("Введите корректное количество вершин");
                return;
            }

            matrix = new int[n, n];

            dataGridView1.ColumnCount = n;
            dataGridView1.RowCount = n;

            listBox2.Items.Clear();
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            dataGridView1.Rows.Clear();
            listBox1.Items.Clear();
            listBox2.Items.Clear();
        }

        private void FindIsolatedVertices()
        {
            int n = matrix.GetLength(0);

            for (int i = 0; i < n; i++)
            {
                bool isolated = true;

                for (int j = 0; j < n; j++)
                {
                    if (matrix[i, j] != 0 || matrix[j, i] != 0)
                    {
                        isolated = false;
                        break;
                    }
                }

                if (isolated)
                    listBox1.Items.Add($"Вершина {i} изолирована");
            }
        }

        private void btnCheck_Click(object sender, EventArgs e)
        {
            try
            {
                int n = dataGridView1.RowCount;
                matrix = new int[n, n];

                for (int i = 0; i < n; i++)
                {
                    for (int j = 0; j < n; j++)
                    {
                        matrix[i, j] = Convert.ToInt32(dataGridView1[j, i].Value);
                    }
                }

                listBox1.Items.Clear();
                FindIsolatedVertices();
            }
            catch
            {
                listBox2.Items.Add("Ошибка ввода матрицы");
            }
        }
    }
}