poj 1979 Red and Black 【dfs】

Red and Black

Time Limit: 1000MS Memory Limit: 30000KTotal Submissions: 26825 Accepted: 14576

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

45596
13
代码：
#include<stdio.h>#include<string.h>char map[25][25];int sum,m,n;int dfs(int x,int y){int i,j;if(map[x][y]=='#')return sum;if(x<0||x>=m||y<0||y>=n)return sum;else{sum++;map[x][y]='#';dfs(x,y+1);dfs(x,y-1);dfs(x-1,y);dfs(x+1,y);}}int main(){int i,j,x,y;while(scanf("%d%d",&n,&m),n|m){for(i=0;i<m;i++){scanf("%s",map[i]);for(j=0;j<n;j++){if(map[i][j]=='@'){x=i;y=j;}}}sum=0;dfs(x,y);printf("%d\n",sum);}return 0;}