迷宫的最短路径--BFS

import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
class P {
	int x;
	int y;
	public P(int a, int b) {
		this.x = a;
		this.y = b;
	}
}
public class Main {
	static final int INF = -1;
	static char[][] arr;
	static int[][] dis;
	static int[] tempx = { 1, 0, -1, 0 };
	static int[] tempy = { 0, 1, 0, -1 };
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int M = sc.nextInt();
		int sx = 0, sy = 0, gx = 0, gy = 0;
		arr = new char[N][M];
		dis = new int[N][M];
		for (int i = 0; i < N; i++) { 		                  	// 输入 以及得到sx sy 的地址
			String str = sc.next();
			arr[i] = str.toCharArray();
			for (int x = 0; x < str.length(); x++) {
				dis[i][x] = INF; 			                               	// 把所有位置初始化为INF 初始化
				if (str.charAt(x) == 'S') {	
					sx = i;
					sy = x;
				}
				if (str.charAt(x) == 'G') {
					gx = i;
					gy = x;
				}
			}
		}
		dis[sx][sy] = 0;			                                          			//将起点设置为 0
		Queue<P> que = new LinkedList<P>();		            //创建一个队列
		que.offer(new P(sx, sy));			                              	//直接扔到队列里面
//		System.out.println(sx + " " + sy + " " + gx + " " + gy);
		while (que.size() > 0) {
			P p = que.poll();				                                          	//poll队列的头
			if (p.x == gx && p.y == gy)		                               	//到达终点跳出来
				break;
 
			for (int i = 0; i < 4; i++) {		                                   //四个方向
				int nx = p.x + tempx[i];
				int ny = p.y + tempy[i];
 
				if (nx >= 0 && nx < N && ny >= 0 && ny < M && dis[nx][ny] == INF && arr[nx][ny] != '#') {
					que.offer(new P(nx, ny));
					dis[nx][ny] = dis[p.x][p.y] + 1;
				}
			}
		}
		System.out.println(dis[gx][gy]);
	}
}