Java实现广度优先遍历bfs

import java.util.*;

public class Main{
    static int N=210;
    static int r ,c;;//必须在函数外定义为静态 r为行,c为列 方便下面使用
    static int[][] dist = new int[N][N];
    static char[][] f = new char [N][N];
    static Queue<AbstractMap.SimpleEntry<Integer,Integer>> queue = new ArrayDeque<>();// 理解为设置一个队列 先进先出 

    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int t = in.nextInt();
        while(t-->0){
            r = in.nextInt();
            c = in.nextInt();
            for(int i=0;i<r;i++){
                f[i] = in.next().toCharArray(); //因为这里指针从零开始 下面索引也要从零开始!!!!
            }
            int m=0,n=0;
            for(int i=0;i<r;i++){
                for(int j=0;j<c;j++){
                    dist[i][j] = -1;
                    if(f[i][j] == 'S'){
                        m=i;n=j;
                    }
                }
            }
            bfs(m,n);




        }

    }
    public static void bfs(int i,int j){
        queue.add(new AbstractMap.SimpleEntry<>(i,j));
        int[] x = {-1,0,1,0};
        int[] y = {0,1,0,-1};
        f[i][j]='#';
        dist[i][j]=0;
        while(!queue.isEmpty()){//为空说明无路可走 
            int x1,y1;
            AbstractMap.SimpleEntry<Integer, Integer> remove = queue.remove();
            for(int z=0;z<4;z++){
                x1 = remove.getKey()+x[z];
                y1 = remove.getValue()+y[z];
                if(x1<r&&x1>=0&&y1<c&&y1>=0&&f[x1][y1]!='#'&&dist[x1][y1]==-1){  //注意边界问题
                    if(f[x1][y1]=='.'){
                        dist[x1][y1]=dist[remove.getKey()][remove.getValue()]+1;
                        f[x1][y1]='#';
                        queue.add(new AbstractMap.SimpleEntry<>(x1,y1));
                    }
                    if(f[x1][y1]=='E'){
                        dist[x1][y1]=dist[remove.getKey()][remove.getValue()]+1;
                        queue.add(new AbstractMap.SimpleEntry<>(x1,y1));
                        System.out.println(dist[x1][y1]);
                        queue.clear(); //多组数据 需要及时清理
                        return;
                    }

                }

            }
        }
        if(queue.isEmpty()){
            queue.clear();
            System.out.println("oop!");
            return;
        }

    }
}