（java）簡單回朔法解決迷宮問題

import java.util.*;
class Step{
    int x,y,d;
    public Step(int x,int y,int d) {
        this.x = x;//橫座標
        this.y = y;//縱座標
        this.d = d;//方向
    }
}

public class Main3 {

	public static int getnum(int x1,int y1,int x2,int y2){
		return (x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
	}
    public static void main(String[] args) {
    	Scanner sc=new Scanner(System.in);
    	while(sc.hasNextInt()){
    		//構造迷宮
    		int n=sc.nextInt();
    		int m=sc.nextInt();
    		int[][] maze=new int[n][m];
    		ArrayList<int[][]> list = new ArrayList<int[][]>();
    		 for(int i = 0; i < n; ++i) {
    			 String str=sc.next();
    	            for(int j = 0; j < m; ++j) {
    	                char  c= str.charAt(j);
    	                if(c=='.'){
    	                	 maze[i][j] = 0;
    	                	 int[][] endij=new int[1][2];
    	                	 endij[0][0]=i+1;
    	                	 endij[0][1]=j+1;
    	                	 list.add(endij);
    	                }else{
    	                	 maze[i][j] = 1;
    	                } 	
    	            }
    	        }
    		 int begini=sc.nextInt()+1;
    		 int beginj=sc.nextInt()+1;
    		 int max=0;
    		 int endi=0;
    		 int endj=0;
    		 for(int i=0;i<list.size();i++){
    			 int temp=getnum(list.get(i)[0][0],list.get(i)[0][1],begini,beginj);
    			 if(temp>max){
    				 max=temp;
    				 endi=list.get(i)[0][0];
    				 endj=list.get(i)[0][1];
    			 }
    		 }
    		int k=sc.nextInt();
    		int[][] move=new int[k][2];
    		for(int i=0;i<k;i++){
    			for(int j=0;j<2;j++){
    				move[i][j]=sc.nextInt();
    			}
    		}
        Stack s = new Stack();
        Stack s1 = new Stack();
        int a = path(maze, move, s,begini,beginj,endi,endj);
        if(s.isEmpty()){
        	System.out.println("-1");
        }else{
        	System.out.println(s.size());
        }
    	}
    }
    
    public static int path(int[][] maze,int[][] move,Stack s,int begini,int beginj,int endi,int endj){
        Step temp = new Step(begini,beginj,-1); //起點
        s.push(temp);
        while(!s.isEmpty()){
            temp = (Step) s.pop();
            int x = temp.x;
            int y = temp.y;
            int d = temp.d+1;
            while(d<move.length){
                int i = x + move[d][0];
                int j = y + move[d][1];
                if(i<=maze.length-1 && j<=maze[0].length-1 && maze[i][j] == 0){    //該點可達
                    temp = new Step(i,j,d); //到達新點
                    s.push(temp);
                    x = i;
                    y = j;
                    maze[x][y] = -1;  //到達新點，標誌已經到達
                    if(x == endi && y == endj){
                        return 1;  //到達出口，迷宮有路，返回1
                    }else{
                        d = 0;  //重新初始化方向
                    }
                }else{
                    d++; //改變方向
                }
            }
        }
        return 0;
    }

}