[백준] 2589번 보물섬 (gold 5

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

class Point{
    int x;
    int y;
    int v;
    public Point(int x, int y, int v){
        this.x=x;
        this.y=y;
        this.v=v;
    }
}
public class Main{
    static int[] numx={-1,1,0,0};
    static int[] numy={0,0,-1,1};
    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());
        int n=Integer.valueOf(st.nextToken());
        int m=Integer.valueOf(st.nextToken());

        char[][] map=new char[n+1][m+1];

        for(int i=1; i<=n; i++){
            String a=br.readLine();
            for(int j=1; j<=m; j++){
                map[i][j]=a.charAt(j-1);
            }
        }

        Queue<Point> que=new LinkedList<>();
        int min=0;
        for(int i=1; i<=n; i++){
            for(int j=1; j<=m; j++){
                if(map[i][j]=='W'){
                    continue;
                }
                que.clear();
                boolean[][] visit=new boolean[n+1][m+1];
                visit[i][j]=true;
                que.offer(new Point(j,i,0));
                while(!que.isEmpty()){
                    Point temp=que.poll();
                    min= min<temp.v ? temp.v : min;

                    for(int k=0; k<4; k++) {
                        int tx = temp.x + numx[k];
                        int ty = temp.y + numy[k];

                        if (tx < 1 || tx > m || ty < 1 || ty > n || map[ty][tx] == 'W' || visit[ty][tx]) {
                            continue;
                        }
                        visit[ty][tx] = true;
                        que.offer(new Point(tx, ty, temp.v + 1));
                    }

                }
            }
        }
        bw.write(min+"");
        bw.flush();
    }
}



// 항상 모든 케이스들의 최단경로를 구하면서 비교하는 문제.
// 어딘가를 경유하는 걸 고려할 필요x
// 너비탐색으로 다른 점에 도달할때마다가 최단의 거리임.