hdu-1312

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. 

InputThe 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) 
OutputFor 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

AC代码为：

#include<cstdio>#include<iostream>#include<cmath>#include<cstring>using namespace std;int sum,H,W;int dx[4]={1,0,-1,0};int dy[4]={0,1,0,-1};char str[21][21];int vis[21][21];void f(int xl,int yl){vis[yl][xl]=1;sum++;for(int i=0;i<4;i++){int cx=xl+dx[i];int cy=yl+dy[i];if(cx>=0 && cx<W && cy>=0 && cy<H && !vis[cy][cx] && str[cy][cx]!='#')f(cx,cy);}}int main(){int x,y;while(~scanf("%d%d",&W,&H)){if(H==0 || W==0)break;for(int i=0;i<H;i++){scanf("%s",str[i]);}for(int i=0;i<H;i++){for(int j=0;j<W;j++)if(str[i][j]=='@'){x=j;y=i;}}sum=0;memset(vis,0,sizeof(vis));f(x,y);printf("%d ",sum);}return 0;}