Ali test written test-team problem

Code: Similar to depth-first traversal

package ali;

import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {

	/** 请完成下面这个函数，实现题目要求的功能 **/
	/** 当然，你也可以不按照这个模板来作答，完全按照自己的想法来 ^-^ **/
	static int findCircleNum(int[][] M) {
		Set<Integer> set = new HashSet<Integer>();
		int num = 0;
		int index = 0;
		while (set.size() != M.length && index < M.length) {
			if (!set.contains(index)) {
				for (int i = index; i < M.length; i++) {
					if (M[index][i] == 1)
						set.add(i);
				}
				num++;
			} else {
				for (int i = index; i < M.length; i++) {
					if (M[index][i] == 1)
						set.add(i);
				}
			}
			index++;
		}
		return num;

	}

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int res;

		int _M_rows = 0;
		int _M_cols = 0;
		_M_rows = Integer.parseInt(in.nextLine().trim());
		_M_cols = Integer.parseInt(in.nextLine().trim());

		int[][] _M = new int[_M_rows][_M_cols];
		for (int _M_i = 0; _M_i < _M_rows; _M_i++) {
			String row_x = String.valueOf(in.nextLine().trim());
			String[] row_y = row_x.split(",");
			for (int _M_j = 0; _M_j < _M_cols; _M_j++) {
				_M[_M_i][_M_j] = Integer.parseInt(row_y[_M_j]);

			}
		}

		if (in.hasNextLine()) {
			in.nextLine();
		}

		res = findCircleNum(_M);
		System.out.println(String.valueOf(res));

	}
}