HDU 1241 Oil Deposits

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本文介绍了一种用于探测地下油藏的算法，通过分析网格中各区块的油藏信息，确定不同油藏的数量。使用深度优先搜索算法遍历网格，识别并计数相连的油藏区块。

Oil Deposits

https://vjudge.net/problem/HDU-1241
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

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

Sample Output

0
1
2
2

C++

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int MAXN = 105;
char maze[MAXN][MAXN];
bool vis[MAXN][MAXN];
int n, m;

bool judge(int x, int y)
{
	return x >= 0 && x < n && y >= 0 && y < m;
}

void dfs(int x, int y)
{
	vis[x][y] = true;
	for(int i = -1; i <= 1; i ++){
		for(int j = -1; j <= 1; j ++){
			int tx = x + i;
			int ty = y + j;
			if(judge(tx, ty) && !vis[tx][ty] && maze[tx][ty] == '@')
				dfs(tx, ty);
		}
	}
}

int main()
{
	while(scanf("%d%d", &n, &m) != EOF)
	{
		if(n == 0 && m == 0) break;
		for(int i = 0; i < n; i ++)
			scanf("%s", maze[i]);
		memset(vis, false, sizeof(vis));
		int ans = 0;
		for(int i = 0; i < n; i ++){
			for(int j = 0; j < m; j ++){
				if(maze[i][j] == '@' && !vis[i][j]){
					ans ++;
					dfs(i, j);
				}
			}
		}
		printf("%d\n", ans);
	}
	return 0;	
}

Java

import java.util.Scanner;

public class Main {
	
	static int MAXN = 105;
	static boolean vis[][] = new boolean[MAXN][MAXN];
	static char maze[][] = new char[MAXN][MAXN];
	static int n, m;
	
	static boolean judge(int x, int y){
		if(x < 0 || x >= n || y < 0 || y >= m) return false;
		return true;
	}
	
	public static void main(String args[]){
		Scanner cin = new Scanner(System.in);
		while(cin.hasNext()){
			n = cin.nextInt();
			m = cin.nextInt();
			cin.nextLine();
			if(n == 0 && m == 0) break;
			String s;
			for(int i = 0; i < n; i ++){
				for(int j = 0; j < m; j ++){
					vis[i][j] = false;
				}
			}
			for(int i = 0; i < n; i ++){
				s = cin.nextLine();
				maze[i] = s.toCharArray();
			}
			int ans = 0;
			for(int i = 0; i < n; i ++){
				for(int j = 0; j < m; j ++){
					if(maze[i][j] == '@' && !vis[i][j]){
						ans ++;
						dfs(i, j);
					}
				}
			}
			System.out.println(ans);
			
		}
		cin.close();
	}
	
	static void dfs(int x, int y){
		vis[x][y] = true;
		for(int i = -1; i <= 1; i ++){
			for(int j = -1; j <= 1; j ++){
				int tx = x + i;
				int ty = y + j;
				if(judge(tx, ty) && !vis[tx][ty] && maze[tx][ty] == '@'){
					dfs(tx, ty);
				}
			}
		}
	}
}