杭电1312 red and black

Red and Black
Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 8694    Accepted Submission(s): 5393


Problem Description
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
4559613

#include<stdio.h>#include<string.h>char map[21][21];int dx[4]={0,0,1,-1},dy[4]={1,-1,0,0};  int n,m,t,visit[21][21];void dfs(int xx,int yy){      int x,y,l;        for(l=0;l<4;l++)        {            x=xx+dx[l];            y=yy+dy[l];            if(x>=0&&x<n&&y>=0&&y<m&&map[x][y]=='.'&&visit[x][y]==0)            {                visit[x][y]=1;                    t++;                dfs(x,y);            }        }    }main(){    int i,j;    while(scanf("%d%d",&m,&n)&&!(m==0&&n==0))    {        getchar();            memset(visit,0,sizeof(visit));        for(i=0;i<n;i++)        {        for(j=0;j<m;j++)        scanf("%c",&map[i][j]);       getchar();     }     for(i=0;i<n;i++)        for(j=0;j<m;j++)         if(map[i][j]=='@')        {            t=1;          visit[i][j]=1;     dfs(i,j);        }        printf("%d\n",t);}}