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

 1 #include <iostream>
 2 #include <cstdio>
 3 using namespace std;
 4 char a[21][21];
 5 int m,n;
 6 int count=0;
 7 void dfs(int x,int y)
 8 {
 9     if(a[x][y]==‘.‘&&x<n&&x>=0&&y<m&&y>=0)
10     {
11         count++;
12         a[x][y]=‘#‘;
13         dfs(x+1,y);
14         dfs(x,y+1);
15         dfs(x,y-1);
16         dfs(x-1,y);
17     }
18 }
19 int main()
20 {
21     freopen("in.txt","r",stdin);
22     while(scanf("%d%d",&m,&n)&&m!=0&&n!=0)
23     {
24         count=0;
25         int i,j,x,y;
26         for(i=0;i<n;i++)
27         {
28             for(j=0;j<m;j++)
29             {
30                 cin>>a[i][j];
31                 if(a[i][j]==‘@‘)
32                 {
33                     x=i;y=j;
34                 }
35             }
36         }
37         a[x][y]=‘.‘;
38         dfs(x,y);
39         cout<<count<<endl;
40     }
41 }