백준 2667번 - 단지번호붙이기

https://www.acmicpc.net/problem/2667

2667번: 단지번호붙이기

# 문제풀이 

-  bfs로 푸는 문제 이며, 단지 수를 저장할대 ArrayList를 통해 넣었다.

-  Collections.sort로 정렬하는 것을 여기서 알게됨 

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

public class Main {

	static int[][] map;
	static boolean[][] visited;
	static int[] dy = { -1, 0, 1, 0 };
	static int[] dx = { 0, 1, 0, -1 };
	static int N, cnt, ans;
	static Queue<Point> que;
	static ArrayList<Integer> al;

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		N = sc.nextInt();
		map = new int[N][N];
		visited = new boolean[N][N];
		que = new LinkedList<>();
		cnt = 0;
		ans = 0;
		al = new ArrayList<>();
		for (int i = 0; i < N; i++) {
			String str = sc.next();
			for (int j = 0; j < N; j++) {
				map[i][j] = str.charAt(j) - '0';
			}
		}

		for (int i = 0; i < N; i++) {
			for (int j = 0; j < N; j++) {
				if (map[i][j] == 1) {
				
					bfs(i, j);
					cnt++;

				}
			}
		}
		Collections.sort(al);
		System.out.println(cnt);
		for (int i = 0; i < al.size(); i++) {
			System.out.println(al.get(i));
		}
	}

	private static void bfs(int y, int x) {

		que.offer(new Point(y, x));
		visited[y][x] = true;
		while (!que.isEmpty()) {
			
			Point p = que.poll();
			ans++;
			for (int k = 0; k < 4; k++) {
				int ny = p.y + dy[k];
				int nx = p.x + dx[k];
				if (ischecked(ny, nx) && !visited[ny][nx] && map[ny][nx] == 1) {

					visited[ny][nx] = true;
					map[ny][nx] = 0;
					
					que.offer(new Point(ny, nx));
				}
			}

		}
		al.add(ans);
		ans = 0;
	}

	private static boolean ischecked(int my, int mx) {
		if (my >= 0 && my < N && mx >= 0 && mx < N) {
			return true;
		}
		return false;
	}

	static class Point {
		int y;
		int x;

		public Point(int y, int x) {
			super();
			this.y = y;
			this.x = x;
		}
	}

	static void print() {
		for (int i = 0; i < N; i++) {

			for (int j = 0; j < N; j++) {
				System.out.print(map[i][j]);
			}
			System.out.println();
		}
		System.out.println();
	}
}