Oil Deposits【深搜】

最新推荐文章于 2020-02-04 18:54:19 发布

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本文介绍了一种用于探测地下油井的算法，通过分析网格中各点的状态，确定不同油井的数量。采用深度优先搜索（DFS）算法遍历网格，标记相连的油井为同一油井，最终统计独立油井总数。

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Oil Deposits

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

题意：@代表油井，@相连代表处于同一油井中，问有几个油井

方法：深搜的模板题，不需要回溯

AC代码

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <map>
#include <stack>
#include <queue>
#include <vector>
#include <bitset>
#include <set>
#include <utility>
using namespace std;
typedef long long ll;
#define inf 0x3f3f3f3f
#define rep(i,l,r) for(int i=l;i<=r;i++)
#define lep(i,l,r) for(int i=l;i>=r;i--)
#define ms(arr) memset(arr,0,sizeof(arr))
//priority_queue<int,vector<int> ,greater<int> >q;
const int maxn = (int)1e5 + 5;
const ll mod = 1e9+7;
bool vis[120][120];
char mapp[120][120];
int nextx[8]={1,1,1,0,-1,-1,-1,0};
int nexty[8]={1,0,-1,-1,-1,0,1,1};
int n,m;
int num;
void dfs(int x,int y)
{
	int dx,dy;
	for(int k=0;k<8;k++)
	{
		dx=x+nextx[k];
		dy=y+nexty[k];
		if(mapp[dx][dy]!='@'||dx<0||dy<0||dx>n||dy>m||vis[dx][dy]==true)
			continue;
		vis[dx][dy]=true;
		dfs(dx,dy);
	}
	return ;
}
int main() 
{
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);
    ios::sync_with_stdio(0),cin.tie(0);
    while(scanf("%d %d",&n,&m)&&n+m)
    {
    	memset(vis,false,sizeof(vis));
    	num=0;
   		rep(i,1,n) {
   			scanf("%s",mapp[i]+1);
   		}
   		rep(i,1,n) {
   			rep(j,1,m) {
   				if(mapp[i][j]=='@'&&vis[i][j]==false)
   				{
   					vis[i][j]=true;
   					num++;
   					dfs(i,j);
/*   					rep(i,1,n) {
			   			rep(j,1,m) {
			   				printf("%d ",vis[i][j]);
	   					}
			   			printf("\n");
			   		}*/
   				}
   			}
   		}

   		printf("%d\n",num);
    }
    return 0;
}