package question;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/*
 @author: Roderland
 @create: 2020年09月16日---10:17
*/
public class Question841 {

 public static void main(String[] args) {
 int[][] a = new int[][]{{1},{2},{3},{}};
 List<Integer> l1 = new ArrayList<>(); l1.add(1);
 List<Integer> l2 = new ArrayList<>(); l2.add(2);
 List<Integer> l3 = new ArrayList<>(); l3.add(3);
 List<Integer> l4 = new ArrayList<>();
 List<List<Integer>> rooms = new ArrayList<>();
 boolean b = Collections.addAll(rooms, l1, l2, l3, l4);
 System.out.println(new Question841().canVisitAllRooms(rooms));
 }

 List<List<Integer>> rooms;
 boolean[] flags;
 public boolean canVisitAllRooms(List<List<Integer>> rooms) {
 this.rooms=rooms;
 flags=new boolean[rooms.size()];
 fun(rooms.get(0), 0);
 for (boolean flag : flags) {
 if (!flag) return false;
 }
 return true;
 }

 public void fun(List<Integer> room, int key) {
 flags[key]=true;
 for (Integer keys : room) {
 if (!flags[keys]) {
 fun(rooms.get(keys), keys);
 }
 }
 }
}