HDU 1312 Red and Black

 1 //#define LOCAL
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 using namespace std;
 6 
 7 int dir[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
 8 char map[23][23];
 9 int m, n, Sx, Sy, cnt;
10 
11 void DFS(int x, int y)
12 {
13     map[x][y] = ‘#‘;
14     for(int i = 0; i < 4; ++i)
15     {
16         int xx = x + dir[i][0];
17         int yy = y + dir[i][1];
18         if(xx>=0 && xx<m && yy>=0 && yy<n
19             && map[xx][yy] == ‘.‘)
20         {
21             ++cnt;
22             map[xx][yy] = ‘#‘;
23             DFS(xx, yy);
24         }
25     }
26 }
27 
28 int main(void)
29 {
30     #ifdef LOCAL
31         freopen("1312in.txt", "r", stdin);
32     #endif
33 
34     while(scanf("%d%d", &n, &m) == 2)
35     {
36         if(m == 0 && n == 0)
37             break;
38         int i, j;
39         getchar();
40         for(i = 0; i < m; ++i)
41         {
42             for(j = 0; j < n; ++j)
43             {
44                 scanf("%c", &map[i][j]);
45                 if(map[i][j] == ‘@‘)
46                 {
47                     Sx = i;
48                     Sy = j;
49                 }
50             }
51             getchar();
52         }
53         map[Sx][Sy] = ‘#‘;
54         cnt = 1;
55         DFS(Sx, Sy);
56         printf("%d\n", cnt);
57     }
58     return 0;
59 }