POJ1979迷宫问题DFS

题目大意：从@出发能到达多少个点。

public class SimDFS {
	//定义走法
	public static int[][] Dxy={{0,-1}, {0, 1}, {1, 0}, {-1, 0}};
	public static final int MAX = 20;
	public static int col;
	public static int row;
	public static char[][] maze = new char[MAX][MAX];
	public static void main(String[] args) {
		Scanner scanner =  new Scanner(System.in);
		col = scanner.nextInt();
		row = scanner.nextInt();
		int x=0,y=0;
		while(col!=0&&row!=0){
			int ans = 1;//起点自带一个
			for(int i = 0; i < row ;++i){
				String temp = scanner.next();
				for(int j = 0 ; j < col;++j){
					char s =temp.charAt(j);
					maze[i][j] = s;
					if(s=='@'){
						x = j;	
						y = i;
					}
				}
			}
			ans += dfs(x,y);
			System.out.println(ans);
			col = scanner.nextInt();
			row = scanner.nextInt();
		}
	}

	private static int dfs(int x, int y) {
		int ans = 0 ;
		for(int d = 0; d < 4; ++d ){
			int new_x = x + Dxy[d][0];//上下右左
			int new_y = y + Dxy[d][1];
			if(new_x >= 0&& new_y >= 0&& new_x < col && new_y < row && maze[new_y][new_x]=='.'){
				maze[new_y][new_x] = '#';//改变走过的位置
				ans  += 1 + dfs(new_x,new_y);
			}
		}
		return ans;
	}

}