POJ 1979 Red and Black

Red and Black

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

代码

#include<cstdio>

using namespace std;

int N,M,arr;
char filed[1005][1005];

void dfs(int x,int y){
    arr++;
    filed[x][y]='1';        \\四个方向
    if(x-1>=0 && x-1<N && y>=0 && y<M && filed[x-1][y]=='.'){
        dfs(x-1, y);
    }
    if(x+1>=0 && x+1<N && y>=0 && y<M && filed[x+1][y]=='.'){
        dfs(x+1,y);
    }
    if(x>=0 && x<N && y-1>=0 && y-1<M && filed[x][y-1]=='.'){
        dfs(x,y-1);
    }
    if(x>=0 && x<N && y+1>=0 && y+1<M && filed[x][y+1]=='.'){
        dfs(x,y+1);
    }
    return ;
}

int main(){
    while(1){
        scanf("%d %d",&M,&N);
        if(N==0 && M==0)
            break;
        arr=0;
        for(int i=0;i<N;i++)
            scanf("%s",filed[i]);
        for(int i=0;i<N;i++)
            for(int j=0;j<M;j++){
                if(filed[i][j]=='@'){
                    dfs(i,j);
                    }
                }
        printf("%d\n",arr);
    }
    return 0;
}