ZOJ Problem Set - 2165 Red and Black

ZOJ Problem Set - 2165

Red and Black

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Time Limit: 2 Seconds        Memory Limit: 65536 KB

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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<iostream>
#include<stdio.h>
#include<string.h>
#define MAX 30
using namespace std;
char map[MAX][MAX];
int count=0;
int w,h;
int dir[4][2]={{0,-1},{-1,0},{0,1},{1,0}};
void dfs(int r,int c)
{
//	cout<<"r: "<<r<<" c: "<<c<<endl;
	//getchar();
	if(r<=0||c<=0||r>h||c>w)
	{
		return;
	}
	map[r][c]='#';
	for(int i=0;i<4;i++)
	{
		if(map[r+dir[i][0]][c+dir[i][1]]=='.')
		{
		//	map[r+dir[i][0]][c+dir[i][1]]='#';
			count++;
			dfs(r+dir[i][0],c+dir[i][1]);
		//	map[r+dir[i][0]][c+dir[i][1]]='.';
		}
	}
}
int main()
{
	while(cin>>w>>h)
	{
		if(w==0||h==0)break;
		int sr,sc;
		count=0;
		memset(map,0,sizeof(map));
		for(int i=1;i<=h;i++)
		{
			for(int j=1;j<=w;j++)
			{
				cin>>map[i][j];
				if(map[i][j]=='@')
				{
					sr=i;sc=j;
				}
			}
		}
		map[sr][sc]='#';
		//cout<<"Mark #1"<<endl;
		dfs(sr,sc);
		cout<<count+1<<endl;
	}
}