hdu1312 red and black 【递归】

Red and Black

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 13080    Accepted Submission(s): 8109

Problem 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)

 

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

4559613
 
【代码】
#include<stdio.h>#include<string.h>#include<algorithm>using namespace std;char a[22][22];int n,m,cnt;void dfs(int x,int y){if(x<1||x>m||y<1||y>n)   return ;if(a[x][y]=='#')   return ;cnt++;a[x][y]='#';dfs(x+1,y);dfs(x-1,y);dfs(x,y-1);dfs(x,y+1);}int main(){int x,y,i,j;while(scanf("%d%d",&n,&m),m|n){cnt=0;for(i=1;i<=m;i++){getchar();for(j=1;j<=n;j++){scanf("%c",&a[i][j]);if(a[i][j]=='@')  x=i,y=j;}}dfs(x,y);printf("%d\n",cnt);}return 0;}