Red and Black
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)
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
题解如下
#include <cstdio> #include <cstdlib> #include <algorithm> #include <iostream> #include <cstring> #include <string> #include <cmath> using namespace std; int w,h,sx,sy,ans; char map[21][21]; int dx[4]={0,0,1,-1}; int dy[4]={1,-1,0,0}; bool v[21][21]; int a[410]; void dfs(int x,int y) { for(int i=0;i<=3;i++) { int tx=x+dx[i],ty=y+dy[i]; if(tx>=1&&tx<=h&&ty>=1&&ty<=w&&map[tx][ty]!='#'&&v[tx][ty]==0) { ans++; v[tx][ty]=1; dfs(tx,ty); } } } int main() { while(cin>>w>>h&&w!=0&&h!=0) { ans=0; for(int i=1;i<=h;i++) for(int j=1;j<=w;j++) { cin>>map[i][j]; if(map[i][j]=='@') { sx=i; sy=j; } } memset(v,0,sizeof(v)); v[sx][sy]=1; dfs(sx,sy); cout<<ans+1<<endl; } return 0; }