HDU 1312（搜索题，DFS）

Red and Black

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 1402    Accepted Submission(s): 904

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

45 59 6 13

#include using namespace std; char a[25][25]; int flag[25][25]; int sum; void DFS(int x,int y) { if(a[x-1][y]=='.' && flag[x-1][y]==0) { sum++; flag[x-1][y]=1; DFS(x-1,y); } if(a[x][y-1]=='.' && flag[x][y-1]==0) { sum++; flag[x][y-1]=1; DFS(x,y-1); } if(a[x][y+1]=='.' && flag[x][y+1]==0) { sum++; flag[x][y+1]=1; DFS(x,y+1); } if(a[x+1][y]=='.' && flag[x+1][y]==0) { sum++; flag[x+1][y]=1; DFS(x+1,y); } } int main() { int n,m,i,j; while(scanf("%d%d",&m,&n),m+n) { getchar(); sum=0; memset(flag,0,sizeof(flag)); memset(a,'#',sizeof(a)); for(i=1;i<=n;i++) { for(j=1;j<=m;j++) { scanf("%c",&a[i][j]); } getchar(); } for(i=1;i<=n;i++) { for(j=1;j<=m;j++) { if(a[i][j]=='@') { sum++; flag[i][j]=1; DFS(i,j); i=n; j=m; } } } printf("%d/n",sum); } return 0; }