图的BFS----迷宫问题

题目描述：

...11111111111111111111111111111
11.111111........1111111111.1111
11.111111..111.11111111.....1111
11.11111111111.1111111111.111111
11.111111.................111111
11.111111.11111111111.11111.1111
11.111111.11111111111.11111..111
11..........111111111.11111.1111
11111.111111111111111.11....1111
11111.111111111111111.11.11.1111
11111.111111111111111.11.11.1111
111...111111111111111.11.11.1111
111.11111111111111111....11.1111
111.11111111111111111111111.1111
111.1111.111111111111111......11
111.1111.......111111111.1111.11
111.1111.11111.111111111.1111.11
111......11111.111111111.1111111
11111111111111.111111111.111...1
11111111111111...............1.1
111111111111111111111111111111..

如上图的迷宫，入口，出口分别：左上角，右下角
"1"是墙壁，"."是通路
求最短需要走多少步？

代码实现：

 import java.util.LinkedList;
 import java.util.Queue;
 import java.util.Scanner;

 public class 图的bfs_迷宫 {
     public static void main(String[] args) {
         Scanner scanner = new Scanner(System.in);
         int m = 21;
         int n = 32;
         char[][] graph = new char[m][n];
         int[][] vis = new int[m][n];// 标记哪些点已经被访问
         Queue<Node> queue = new LinkedList<>();
         for (int i = 0; i < m; i++) {
             graph[i] = scanner.nextLine().toCharArray();
         }
         // for (int j = 0; j < graph.length; j++) {
         // for (int k = 0; k < graph[j].length; k++) {
         // System.out.print(graph[j][k]);
         // }
         // System.out.println();
         // }

         Node start = new Node(0, 0, 0);
         queue.add(start);
         while (!queue.isEmpty()) {
             Node poll = queue.poll();
             int x = poll.x;
             int y = poll.y;
             int deep = poll.depth;
             vis[x][y] = 1;// 标注为已访问
             // 判断是否到达终点
             if (x == m - 1 && y == n - 1) {// 走到出口
                 System.out.println(poll.depth);
                 break;
             }
             // 加四个邻居
             if (x - 1 >= 0 && vis[x - 1][y] == 0 && graph[x - 1][y] == '.') {
                 queue.add(new Node(x - 1, y, deep + 1));
             }
             if (x + 1 < m && vis[x + 1][y] == 0 && graph[x + 1][y] == '.') {
                 queue.add(new Node(x + 1, y, deep + 1));
             }
             if (y - 1 >= 0 && vis[x][y - 1] == 0 && graph[x][y - 1] == '.') {
                 queue.add(new Node(x, y - 1, deep + 1));
             }
             if (y + 1 < n && vis[x][y + 1] == 0 && graph[x][y + 1] == '.') {
                 queue.add(new Node(x, y + 1, deep + 1));
             }
         }
     }

     static class Node {
         int x;
         int y;
         int depth;

         public Node(int x, int y, int depth) {
             this.x = x;
             this.y = y;
             this.depth = depth;
         }
     }
 }

运行结果：