백준 2583 영역 구하기(JAVA)

문제 설명

https://www.acmicpc.net/problem/2583

 

풀이과정

 직사각형 내부를 1로 표시해서 빈 공간을 DFS로 탐색해서 풀이했다.

 

정답코드

import java.io.*;
import java.util.*;

public class Main {
    static int[] dy = {-1, 1, 0, 0};
    static int[] dx = {0, 0, -1, 1};
    static int[][] board;
    static boolean[][] visited;
    static int N, M, K;
    static int area = 1;
    static List<Integer> list = new ArrayList<>();

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st = new StringTokenizer(br.readLine());

        M = Integer.parseInt(st.nextToken());
        N = Integer.parseInt(st.nextToken());
        K = Integer.parseInt(st.nextToken());

        board = new int[M][N];
        visited = new boolean[M][N];

        for (int i = 0; i < K; i++) {
            st = new StringTokenizer(br.readLine());
            int x1 = Integer.parseInt(st.nextToken());
            int y1 = Integer.parseInt(st.nextToken());
            int x2 = Integer.parseInt(st.nextToken());
            int y2 = Integer.parseInt(st.nextToken());

            for (int j = y1; j < y2; j++) {
                for (int k = x1; k < x2; k++) {
                    board[j][k] = 1;
                }
            }
        }

        for (int i = 0; i < M; i++) {
            for (int j = 0; j < N; j++) {
                if (board[i][j] == 0 && !visited[i][j]) {
                    dfs(i, j);
                    list.add(area);
                    area = 1;
                }
            }
        }

        bw.write(list.size() + "\n");

        Collections.sort(list);
        for (int i = 0; i < list.size(); i++) {
            bw.write(list.get(i) + " ");
        }

        bw.flush();
    }

    public static void dfs(int y, int x) {

        if (visited[y][x]) {
            return;
        }

        visited[y][x] = true;

        for (int i = 0; i < 4; i++) {
            int ny = y + dy[i];
            int nx = x + dx[i];

            if (ny >= 0 && ny < M && nx >= 0 && nx < N) {
                if (board[ny][nx] == 0 && !visited[ny][nx]) {
                    dfs(ny, nx);
                    area++;
                }
            }
        }
    }
}