public class Solution {

    private void dfs(int[,] M, int[] visited, int i)

        {

            for (int j = ; j < M.GetLength(); j++)

            {

                if (M[i, j] ==  && visited[j] == )

                {

                    visited[j] = ;

                    dfs(M, visited, j);

                }

            }

        }

        public int FindCircleNum(int[,] M)

        {

            int[] visited = new int[M.GetLength()];

            int count = ;

            for (int i = ; i < M.GetLength(); i++)

            {

                if (visited[i] == )

                {

                    dfs(M, visited, i);

                    count++;

                }

            }

            return count;

        }

}

public class Solution {

    public int FindCircleNum(int[,] M)

        {

            var N = M.GetLength();

            var groups = N;

            var leads = new int[N];

            for (var i = ; i < N; i++)

            {

                leads[i] = i;

            }

            for (var i = ; i < N; i++)

            {

                for (var j = i + ; j < N; j++)

                {

                    if (M[i, j] == )

                    {

                        var lead1 = find(i, leads);

                        var lead2 = find(j, leads);

                        if (lead1 != lead2)

                        {

                            leads[lead1] = lead2;

                            groups--;

                        }

                    }

                }

            }

            return groups;

        }

        private int find(int x, int[] parents)

        {

            if (parents[x] == x)

            {

                return x;

            }

            else

            {

                return find(parents[x], parents);

            }

        }

}