https://school.programmers.co.kr/learn/courses/30/lessons/43162
import java.util.*;
class Solution {
static int[] visited;
public void DFS(int[][] arr, int d, int n) {
for (int i=0; i<n; i++) {
if (arr[d][i] == 1 && visited[i] == 0) {
visited[i] = 1;
DFS(arr, i, n);
}
}
}
public int solution(int n, int[][] computers) {
int answer = 0;
visited = new int[n];
for (int i=0; i<n; i++) {
if (visited[i] == 0) {
visited[i] = 1;
DFS(computers, i, n);
answer++;
}
}
return answer;
}
}