POJ 1979 Red and Black

Red and Black

Time Limit: 1000MS		Memory Limit: 30000K
Total Submissions: 21143		Accepted: 11292

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) 
The end of the input is indicated by a line consisting of two zeros. 

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
....#.
.....#
......
......
......
......
......
#@...#
.#..#.
11 9
.#.........
.#.#######.
.#.#.....#.
.#.#.###.#.
.#.#..@#.#.
.#.#####.#.
.#.......#.
.#########.
...........
11 6
..#..#..#..
..#..#..#..
..#..#..###
..#..#..#@.
..#..#..#..
..#..#..#..
7 7
..#.#..
..#.#..
###.###
...@...
###.###
..#.#..
..#.#..
0 0

Sample Output

45
59
6
13

Source

Japan 2004 Domestic

 

 

 

#include <cstdio>
char a[22][22];
int w,h;
int f(int i,int j)
{if(i<0||i>=h||j<0||j>=w)
return 0;
if(a[i][j]=='#') return 0;
else {
a[i][j]='#';
return 1+f(i+1,j)+f(i-1,j)+f(i,j+1)+f(i,j-1);
}
}

int main ()
{int i,j;
while(scanf("%d%d",&w,&h),w!=0&&h!=0)
{for(i=0;i<h;i++)
scanf("%s",a[i]);
for(i=0;i<h;i++)
for(j=0;j<w;j++)
if(a[i][j]=='@')
printf("%d\n",f(i,j));
}
return 0;
}

 

DFS=。=居然把==写成=了。“a[i][j]=='#'”