Red and Black--(BFS)

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)

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

#include <stdio.h>
#include <cstring>
#include <queue>
using namespace std;
char a[22][22];
int b[22][22];
int ans;
int w,h;
int fx[2][4]={{1,-1,0,0},{0,0,1,-1}};
struct node{
   int x,y;
};
void bfs(int x,int y)
{
   queue<node> que;
   node e1,e2;
   b[x][y]=1;
   e1.x=x;
   e1.y=y;
   que.push(e1);
   while(que.empty()==0)
   {
       e1=que.front();
       que.pop();
       for(int i=0;i<4;i++)
       {
           int x1=e1.x+fx[0][i];
           int y1=e1.y+fx[1][i];
           if(x1>=0 && x1<h && y1>=0 && y1<w &&a[x1][y1]=='.'&& b[x1][y1]==0)
           {
               ans++;
               e2.x=x1;
               e2.y=y1;
               b[x1][y1]=1;
               que.push(e2);
           }
       }
   }
   printf("%d\n",ans);
}

int main()
{
   while(scanf("%d%d",&w,&h) && w && h)
   {
       memset(a,0,sizeof(a));
       memset(b,0,sizeof(b));
       ans=1;
       for(int i=0;i<h;i++)
       scanf("%s",&a[i]);
       for(int i=0;i<h;i++)
       for(int j=0;j<w;j++)
       {
           if(a[i][j]=='@')
           {
               bfs(i,j);
               break;
               }
           }
   }
   return 0;
}

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