There is a rectangular room, covered with square tiles. Each tile is colored either red or black. A man is standing on a black tile. From a tile, he can move to one of four adjacent tiles. But he can't move on red tiles, he can move only on black tiles.
Write a program to count the number of black tiles which he can reach by repeating the moves described above.
Input
The input consists of multiple data sets. A data set starts with a line containing two positive integers W and H; W and H are the numbers of tiles in the x- and y- directions, respectively. W and H are not more than 20.
There are H more lines in the data set, each of which includes W characters. Each character represents the color of a tile as follows.
'.' - a black tile
'#' - a red tile
'@' - a man on a black tile(appears exactly once in a data set)
The end of the input is indicated by a line consisting of two zeros.
Output
For each data set, your program should output a line which contains the number of tiles he can reach from the initial tile (including itself).
Sample Input
6 9 ....#. .....# ...... ...... ...... ...... ...... #@...# .#..#. 11 9 .#......... .#.#######. .#.#.....#. .#.#.###.#. .#.#..@#.#. .#.#####.#. .#.......#. .#########. ........... 11 6 ..#..#..#.. ..#..#..#.. ..#..#..### ..#..#..#@. ..#..#..#.. ..#..#..#.. 7 7 ..#.#.. ..#.#.. ###.### ...@... ###.### ..#.#.. ..#.#.. 0 0
Sample Output
45 59 6 13
package 递归和回溯;
import java.util.Scanner;
public class Main {
static int map[][];
static int vist[][];
static int dx[]= {0,0,1,-1};
static int dy[]= {1,-1,0,0};
static int n,m;
static int sx,sy;
static int sum;
static void dfs(int x,int y) {
if(x>n||x<1||y>m||y<1)
return ;
for(int i=0;i<4;i++) {
int nx=x+dx[i];
int ny=y+dy[i];
if(nx>n||nx<1||ny>m||ny<1||map[nx][ny]!=1||vist[nx][ny]==1) {
continue;
}else {
sum++;
vist[nx][ny]=1;
dfs(nx,ny);
}
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner sc=new Scanner (System.in);
for(;;) {
m=sc.nextInt();
n=sc.nextInt();
if(n==0&&m==0)
break;
map=new int [n+3][m+3];
vist=new int [n+3][m+3];
sx=0;
sy=0;
sum=1;
for(int i=1;i<=n;i++) {
String s=sc.next();
for(int j=1;j<=m;j++) {
if(s.charAt(j-1)=='.')
map[i][j]=1;
else if(s.charAt(j-1)=='#')
map[i][j]=2;
else if(s.charAt(j-1)=='@'){
map[i][j]=3;
sx=i;
sy=j;
}
}
}
// for(int i=1;i<=n;i++) {
//
// for(int j=1;j<=m;j++) {
//
// System.out.print(map[i][j]);
// }
// System.out.println();
// }
vist[sx][sy]=1;
dfs(sx,sy);
System.out.println(sum);
}
}
}