Poj 1979 Red and Black(DFS)

Red and Black

Time Limit: 1000MS		Memory Limit: 30000K
Total Submissions: 32802		Accepted: 17834

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)
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
#include<stdio.h>
#include<string.h>
int dx[] = {-1,0,0,1};
int dy[] = {0,1,-1,0};
int m,n;
char str[30][30];
int k = 0;
void dfs(int x,int y){
	str[x][y]='#';
	k++;
	for(int i = 0;i < 4;++ i){
		int nx = x + dx[i],ny = y + dy[i];
		if(nx>=0&&nx<n&&ny>=0&&ny<m&&str[nx][ny]=='.'){
			dfs(nx,ny);
		}
	}
	return ;
}

int main()
{
	while(~scanf("%d%d",&m,&n),m){
		memset(str,0,sizeof(str));
		for(int i = 0;i < n;i ++)
			scanf("%s",str[i]);
		for(int i = 0;i < n;i ++){
			for(int j = 0;j < m;j ++){
				if(str[i][j]=='@')
				dfs(i,j);
			}
		}
		printf("%d\n",k);
		k = 0;
	}
return 0;
}