题目：
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.
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.
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
题意描述：
输入矩阵的大小W和H（均小于20）
计算并输出从'@'位置最多能走多少块'.'
解题思路：
输入的时候找到'@'的位置，随后对其进行DFS搜索，下面的代码实现的搜索有点模拟广搜的意思。
代码实现：
1 #include<stdio.h> 2 char map[30][30]; 3 int dfs(int x,int y); 4 int w,h; 5 int main() 6 { 7 int i,j,sx,sy; 8 while(scanf("%d%d",&w,&h),w+h != 0) 9 { 10 for(i=1;i<=h;i++) 11 { 12 for(j=1;j<=w;j++){ 13 scanf(" %c",&map[i][j]); 14 if(map[i][j]=='@') 15 { sx=i;sy=j; } 16 } 17 getchar(); 18 } 19 printf("%d ",dfs(sx,sy)); 20 } 21 return 0; 22 } 23 int dfs(int x,int y) 24 { 25 if(x<1 || x>h || y<1 || y>w) 26 return 0; 27 //如果进入不了dfs函数就是边界问题，注意行数和列数就是x和y的范围 28 if(map[x][y]=='#') 29 return 0; 30 else 31 { 32 map[x][y]='#'; 33 return 1+dfs(x-1,y)+dfs(x+1,y)+dfs(x,y-1)+dfs(x,y+1); 34 } 35 }
易错分析：
1、如果搜索进入不了注意边界的设置问题