Red and Black（水）

Red and Black

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 12138    Accepted Submission(s): 7554

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

 

Sample Output

45

59

6

13

#include <iostream>
#include <cstdio>
using namespace std;
char a[21][21];
int m,n;
int count=0;
void dfs(int x,int y)
{
    if(a[x][y]=='.'&&x<n&&x>=0&&y<m&&y>=0)
    {
        count++;
        a[x][y]='#';
        dfs(x+1,y);
        dfs(x,y+1);
        dfs(x,y-1);
        dfs(x-1,y);
    }
}
int main()
{
    freopen("in.txt","r",stdin);
    while(scanf("%d%d",&m,&n)&&m!=0&&n!=0)
    {
        count=0;
        int i,j,x,y;
        for(i=0;i<n;i++)
        {
            for(j=0;j<m;j++)
            {
                cin>>a[i][j];
                if(a[i][j]=='@')
                {
                    x=i;y=j;
                }
            }
        }
        a[x][y]='.';
        dfs(x,y);
        cout<<count<<endl;
    }
}