给一个矩阵，每个格子上有三种可能，空房，阻碍物或者是保安，阻碍物不能进，空房
四个方向都能进，要写代码给每个空房标记其离最近的保安的距离，比如

000
BGG
B00

B表示障碍物，G表示保安，0表示空房，应该标记为

211
BGG
B11


import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;



public class xddd {

    /**
     * @param args
     */
    class Node{
        int x, y;
        int step;
        Node(int x, int y,  int step){
            this.x = x;
            this.y = y;
            this.step = step;
        }
    }
    
    char[][] martrix ;
    int[][] stepArr = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}}; 
    public xddd() {
        // TODO Auto-generated constructor stub
        martrix = new char[][]{{‘0‘,‘0‘,‘0‘},{‘B‘,‘G‘,‘G‘},{‘B‘,‘0‘,‘0‘}};
    }
    


    public static void printmar(char[][] martrix){
        for(int i=0; i<martrix.length;i++){
            System.out.println(" ");
            for(int j=0; j<martrix[0].length; j++)
                System.out.print(martrix[i][j]);
        }
            
    }
    public int bfs(char[][] martrix, int ix, int iy){
        int[][] visit = new int[3][3];//标记是否已经访问过
        
        Node node = new Node(ix, iy, 0);
        Queue<Node> queue = new LinkedList<Node>();
        queue.offer(node);
        int M = martrix.length;
        int N = martrix[0].length;
        while(!queue.isEmpty()){
            Node head = queue.poll();
            visit[head.x][head.y] = 1;
            for(int i = 0; i < 4; i++){
                int x = head.x + stepArr[i][0];
                int y = head.y + stepArr[i][1];
                //exit
                if(x >= 0 && x < M && y >= 0 && y < N &&martrix[x][y] == ‘G‘){
                    return head.step+1;
                }
                //bfs
                if(x >= 0 && x < M && y >= 0 && y < N &&martrix[x][y] == ‘0‘ && visit[x][y] == 0){
                    
                    System.out.println(x + " " +y + head.step);
                    Node newNode = new Node(x, y, head.step + 1);
                    queue.offer(newNode);
                }

    
            }
        }
        return -1;
    }
    

    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
         xddd x = new xddd();
         printmar(x.martrix);
         char[][] ret = new char[3][3];
            for(int i=0; i<x.martrix.length;i++){
                System.out.println(" ");
                for(int j=0; j<x.martrix[0].length; j++){
                    if(x.martrix[i][j] != ‘0‘)
                        ret[i][j] = x.martrix[i][j];
                    else{
                        ret[i][j] = (char)(‘0‘ + x.bfs(x.martrix,i,j));
                    }
                }
                    
            }
    
             printmar(ret);
    }
    
    


}