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 = 0;
    if(arr[i][j] == '.') 
    {
        res += 1; 
        arr[i][j] = '#';
        if(i > 0) res += f(arr,i - 1,j,w,h);
        if(i < h - 1) res += f(arr,i + 1,j,w,h);
        if(j > 0) res += f(arr,i,j - 1,w,h);
        if(j < w - 1) res += f(arr,i,j + 1,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 == 0 && h == 0) break;
        //cin>>ch;

        char **arr = new char*[h];
        for(i = 0; i < h; ++i) arr[i] = new char[w];

        for(i = 0; i < h; ++i)
        {
            for(j = 0; j < w; ++j)
            {
                cin>>arr[i][j];
            }
            //cin>>ch;
        }

        for(i = 0; i < h; ++i)
        {
            for(j = 0; 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 = 0; i < h; ++i) delete [] arr[i];
        delete [] arr;
    }

    return 0;
}