Red and Black

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)

Total Submission(s): 19524    Accepted Submission(s): 11879

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

....#.

.....#

......

......

......

......

......

#@...#

.#..#. 

 

 

Sample Output

 

45

 

 

题意：

@为起点，可上下左右走，不能走#，问可以走多少.

 

简单DFS

 

附AC代码：

1 #include
     
       2 using namespace std; 3  4 int ans,sx,sy,n,m; 5 char ma[30][30]; 6 int a[4][2]={
   1,0,-1,0,0,1,0,-1}; 7  8 void dfs(int x,int y){ 9     ans++;10     ma[x][y]='#';11     for(int i=0;i<4;i++){12         int tx=x+a[i][0];13         int ty=y+a[i][1];14         if(tx
      
       =0&&ty
       
        =0&&ma[tx][ty]=='.'){15             dfs(tx,ty);16         }17     }18     return ;19 }20 21 int main(){22     while(cin>>n>>m){23         if(n==0&&m==0)24         break;25         ans=0;26         for(int i=0;i
        
         >ma[i][j];29                 if(ma[i][j]=='@'){30                     sx=i;31                     sy=j;32                     //cout<
         <<" "<
          
           <