HDOJ 1312 Red and Black(単純dfs)

Red and Black
Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 13020    Accepted Submission(s): 8062
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

   
   
   
   

    
    
    
    45 59 6 13
   
   
   
   

 
 
単純なdfs、コードは以下の通りです.
 

#include<cstdio>
#include<cstring>
int count,n,m;
char str[22][22];

void dfs(int x,int y)
{
	if(str[x][y]=='#')
	   return ;
	if(x<1||x>n||y<1||y>m)
	   return ;
	count++;
	str[x][y]='#';
	dfs(x,y-1);
	dfs(x-1,y);
	dfs(x,y+1);
	dfs(x+1,y);
}

int main()
{
	int i,j,x,y;
	while(scanf("%d%d",&m,&n)&&n||m)
	{
		count=0;
		for(i=1;i<=n;i++)
		{
			getchar();
			for(j=1;j<=m;j++)
			{
				scanf("%c",&str[i][j]);
				if(str[i][j]=='@')
				{
					x=i;
					y=j;
				}
			}
		}
		dfs(x,y);
		printf("%d
",count);
	}
	return 0;
}