OpenJudge/Poj 1979 Red and Black / OpenJudge 2816 红与黑

1.链接地址：

http://bailian.openjudge.cn/practice/1979

http://poj.org/problem?id=1979

2.题目：

总时间限制:

1000ms

内存限制:

65536kB

描述

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.

输入

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.

输出

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).

样例输入

6 9
....#.
.....#
......
......
......
......
......
#@...#
.#..#.
11 9
.#.........
.#.#######.
.#.#.....#.
.#.#.###.#.
.#.#..@#.#.
.#.#####.#.
.#.......#.
.#########.
...........
11 6
..#..#..#..
..#..#..#..
..#..#..###
..#..#..#@.
..#..#..#..
..#..#..#..
7 7
..#.#..
..#.#..
###.###
...@...
###.###
..#.#..
..#.#..
0 0

样例输出

45
59
6
13

来源

Japan 2004 Domestic

3.思路：

4.代码：

 #include <iostream>
 #include <cstdio>

 using namespace std;

 int f(char **arr,const int i,const int j,int w,int h)
 {
     int res = ;
     if(arr[i][j] == '.')
     {
         res += ;
         arr[i][j] = '#';
         if(i > ) res += f(arr,i - ,j,w,h);
         if(i < h - ) res += f(arr,i + ,j,w,h);
         if(j > ) res += f(arr,i,j - ,w,h);
         if(j < w - ) res += f(arr,i,j + ,w,h);
     }
     return res;
 }

 int main()
 {
     //freopen("C:\\Users\\wuzhihui\\Desktop\\input.txt","r",stdin);

     int i,j;

     int w,h;
     //char ch;
     while(cin>>w>>h)
     {
         if(w ==  && h == ) break;
         //cin>>ch;

         char **arr = new char*[h];
         for(i = ; i < h; ++i) arr[i] = new char[w];

         for(i = ; i < h; ++i)
         {
             for(j = ; j < w; ++j)
             {
                 cin>>arr[i][j];
             }
             //cin>>ch;
         }

         for(i = ; i < h; ++i)
         {
             for(j = ; j < w; ++j)
             {
                 if(arr[i][j] == '@')
                 {
                     arr[i][j] = '.';
                     cout << f(arr,i,j,w,h) << endl;
                     break;
                 }
             }
             if(j < w) break;
         }

         for(i = ; i < h; ++i) delete [] arr[i];
         delete [] arr;
     }

     return ;
 }