Hdu1241 Oil Deposits

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Description

The GeoSurvComp geologic survey company is responsible for detecting underground oil deposits. GeoSurvComp works with one large rectangular region of land at a time, and creates a grid that divides the land into numerous square plots. It then analyzes each plot separately, using sensing equipment to determine whether or not the plot contains oil. A plot containing oil is called a pocket. If two pockets are adjacent, then they are part of the same oil deposit. Oil deposits can be quite large and may contain numerous pockets. Your job is to determine how many different oil deposits are contained in a grid.

Input

The input file contains one or more grids. Each grid begins with a line containing m and n, the number of rows and columns in the grid, separated by a single space. If m = 0 it signals the end of the input; otherwise 1 <= m <= 100 and 1 <= n <= 100. Following this are m lines of n characters each (not counting the end-of-line characters). Each character corresponds to one plot, and is either ‘*’, representing the absence of oil, or ‘@’, representing an oil pocket.

Output

For each grid, output the number of distinct oil deposits. Two different pockets are part of the same oil deposit if they are adjacent horizontally, vertically, or diagonally. An oil deposit will not contain more than 100 pockets.

Sample Input

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1 1
*
3 5
*@*@*
**@**
*@*@*
1 8
@@****@*
5 5 
****@
*@@*@
*@**@
@@@*@
@@**@
0 0

Sample Output

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0
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2

Analysis

DFS板题，求连通区域的数量，从任意一点开始，将遇到的@变成*并从此点开始进行DFS，DFS过程中遇到@进行相同操作后递归，一次DFS完成后会将一个连通区域中的@全部变成*，这样总共进行的DFS次数就是连通区域的个数。

Code

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#include <iostream>
using namespace std;
char field[100][100];
int m, n;
void dfs(int x, int y)
{
	field[x][y] = '*';
	for (int dx = -1; dx <= 1; dx++)
	{
		for (int dy = -1; dy <= 1; dy++)
		{
			int nx = x + dx;
			int ny = y + dy;
			if (0 <= nx && nx < m && 0 <= ny && ny < n&&field[nx][ny] == '@')
			{
				dfs(nx, ny);
			}
		}
	}
	return;
}
int main()
{
	while (cin >> m >> n)
	{
		if (m == 0)
			break;
		int res = 0;
		field[100][100] = { 0 };
		for (int i = 0; i < m; i++)
		{
			for (int j = 0; j < n; j++)
			{
				cin >> field[i][j];
			}
		}
		for (int i = 0; i < m; i++)
		{
			for (int j = 0; j < n; j++)
			{
				if (field[i][j] == '@')
				{
					dfs(i, j);
					res++;
				}
			}
		}
		cout << res << endl;
	}
	return 0;
}