2016HUAS暑假集训训练题 G - Oil Deposits-优快云博客

本文介绍了一个基于深度优先搜索(DFS)的算法，用于检测矩形区域内地下油田的位置与数量。通过将区域划分为多个正方形地块并分析每个地块是否含有石油，算法能够确定不同油田的数量及其分布情况。

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

1 1

3 5

*@*@*

**@**

*@*@*

@@****@*

5 5

****@

*@@*@

*@**@

@@@*@

@@**@

0 0

Sample Output

分析：

本题为一个dfs题寻找图中有几块油田首先依次寻找找到的标记下再寻找下一个直到再也找不到为止题较为简单直接贴AC代码:

#include <iostream>
#include <cstring>
using namespace std;
char a[100][100];
int x,i,j,y;
int t[100][100];

void bfs(int o,int p, int num)  //定义bfs函数
{
    if(o<0||o>=x||p>=y||p<0) return;  //过界就退出
    if(a[o][p]!='@'||t[o][p]!=0) return; //  没有找到或者已经找到过的也退出
      t[o][p] = num;
     for(int i = -1;i <=1;i++)
     {
         for(int j = -1;j <= 1;j++)
        {
          if(i != 0||j != 0)
            {
                bfs(o+i,p+j,num);          //继续寻找下个
            }
        }
     }
}
int main()
{
    int s ;
    while(cin>>x>>y)
    {
        if(x == 0  && y == 0) break;
         memset(t,0,sizeof(t));
        for( i = 0; i < x;i++)
        {
            for(  j = 0; j < y; j++)
            {
              cin>>a[i][j];
            }
        }
          s = 0;
        for(i = 0; i < x; i++)
            for(j = 0; j < y; j++)
            {
             if(t[i][j]==0&&a[i][j]=='@') bfs(i,j,++s); //没有找到过的且是油田 就进入dfs寻找
            }
        cout<<s<<endl;
    }
    return 0;
}