【JAVA】PKU ACM 1979

import java.util.*;
/*      '.'     黑砖
*       '#'     红砖
*       '@'     起始位置
*       '-'     已经经过
*       room[h][w]
*       从左到右为w  
*       从上到下为h 
*/
class Count {
        public int n = 0;
}
public class Main {
        public static void recursion(char[][] room, int h, int w, Count c) {
                for (int i = 0; i < 4; i++) {
                        switch (i) {
                                case 0:         //上
                                        h--;
                                        if (h >= 0 && room[h][w] == '.') {
                                                room[h][w] = '-';
                                                c.n++;
                                                recursion(room, h, w, c);
                                        }
                                        h++;
                                        break;
                                case 1:         //下
                                        h++;
                                        if (h < room.length && room[h][w] == '.') {
                                                room[h][w] = '-';
                                                c.n++;
                                                recursion(room, h, w, c);
                                        }
                                        h--;
                                        break;
                                case 2:         //左
                                        w--;
                                        if (w >= 0 && room[h][w] == '.') {
                                                room[h][w] = '-';
                                                c.n++;
                                                recursion(room, h, w, c);
                                        }
                                        w++;
                                        break;
                                case 3:         //右
                                        w++;
                                        if (w < room[0].length && room[h][w] == '.') {
                                                room[h][w] = '-';
                                                c.n++;
                                                recursion(room, h, w, c);
                                        }
                                        w--;
                                        break;
                        }
                }
        }
        public static void main(String[] args) {
                Scanner cin = new Scanner(System.in);
                int w, h, wl, hl;
                w = h = wl = hl = 0;
                while ((wl = cin.nextInt()) != 0 &&
                                (hl = cin.nextInt()) != 0) {
                        //输入    
                        char[][] room = new char[hl][wl];
                        for (int i = 0; i < hl; i++) {
                                String s = cin.next();
                                for (int j = 0; j < wl; j++) {
                                        room[i][j] = s.charAt(j);
                                        if (room[i][j] == '@') {
                                                h = i;
                                                w = j;
                                        }
                                }
                        }
                        //递归遍历
                        Count c = new Count();
                        room[h][w] = '-';
                        c.n++;
                        recursion(room, h, w, c);
                        //打印结果
                        System.out.println(c.n);
                }
        }
}