백준 14502(연구소)

문제

코드

성공 코드

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

public class Main {
    private static List<ArrayList<Integer>> list = new ArrayList<ArrayList<Integer>>();
    private static List<Integer> startPosition = new ArrayList<>();
    private static int n, m, result;
    private static int isWall[];
    private static int isWallBak[];

    public static void bfs(){
        Queue<Integer> queue = new LinkedList<>();
        for(int i = 0; i < startPosition.size(); i++){
            queue.offer(startPosition.get(i));
        }

        while (!queue.isEmpty()){
            int ing = queue.poll();
            for(int i = 0; i < list.get(ing).size(); i++){
                int next = list.get(ing).get(i);
                if(isWallBak[next] == 0){
                    isWallBak[next] = 2;
                    queue.offer(next);
                }
            }
        }

        int size = 0;
        for(int i = 0; i < m * n; i++){
            if(isWallBak[i] == 0) size++;
        }

        result = Math.max(result, size);
    }

    public static void dfs(int wallCnt){
        if(wallCnt == 3){
            isWallBak = isWall.clone();
            bfs();
        } else{
            for(int i = 0; i < n * m; i++){
                if(isWall[i] == 0){
                    isWall[i] = 1;
                    dfs(wallCnt + 1);
                    isWall[i] = 0;
                }
            }
        }
    }

    public static void main(String[] args) throws IOException {
        // Init
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        n = Integer.parseInt(st.nextToken());
        m = Integer.parseInt(st.nextToken());

        List<ArrayList<Integer>> map = new ArrayList<ArrayList<Integer>>();
        isWall = new int[m * n];
        isWallBak = new int[m * n];

        //init
        for(int i = 0; i < n; i++) {
            StringTokenizer tmp = new StringTokenizer(br.readLine());
            map.add(new ArrayList<>());
            for(int j = 0; j < m; j++) {
                list.add(new ArrayList<>());
                map.get(i).add(Integer.parseInt(tmp.nextToken()));
            }
        }

        for(int i = 0; i < n; i++){
            for(int j = 0; j < m; j++){
                int value = map.get(i).get(j);
                int position = (i * m) + j;
                isWall[position] = value;

                if(value == 2)
                    startPosition.add(position);
                if (j != m - 1) {// 마지막 열 제외
                    list.get(position).add(position + 1);
                    list.get(position + 1).add(position);
                }
                if (i != n - 1) {// 마지막 행 제외
                    list.get(position).add(position + m);
                    list.get(position + m).add(position);
                }
            }
        }

        isWallBak = isWall.clone();
        dfs(0);
        System.out.println(result);
    }