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
题目描述：
分析：
要求走完迷宫，用dfs比较方便。只要把开始的坐标标记出来，使用递归，每递归一次就是走一步，结果加1即可。设置结束条件，如超出地图或走到#结束即可。
代码：
#include<stdio.h> char a[30][30]; int N,M; int res; int dfs(int y,int x) { if(y<0||y>M-1||x<0||x>N-1) return 0; if(a[y][x]==‘#‘) return 0; a[y][x]=‘G‘; res++; for(int dx=-1;dx<=1;dx++) { int nx=x+dx; if(a[y][nx]==‘.‘) { dfs(y,nx); } } for(int dy=-1;dy<=1;dy++) { int ny=y+dy; if(a[ny][x]==‘.‘) { dfs(ny,x); } } return 0; } ? int main() { while(1) { res=0; int p,q; scanf("%d %d",&N,&M); if(N==0&&M==0) break; getchar(); for(int i=0;i<M;i++) { for(int j=0;j<N;j++) { a[i][j]=getchar(); if(a[i][j]==‘@‘) { p=i; q=j; } } getchar(); } dfs(p,q); printf("%d\n",res); } return 0; }
原文：https://www.cnblogs.com/studyshare777/p/12185454.html