C - Oil Deposits 【dfs】

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#ACM #hpu #dfs #算法练习 #应用

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本文介绍了一种通过深度优先搜索(DFS)算法来确定特定区域内地下油藏数量的方法。该方法将区域划分为多个正方形地块，并使用传感设备确定哪些地块含有油藏。相邻的油藏地块被视为同一油藏的一部分。通过DFS遍历这些地块，可以统计出不同油藏的数量。

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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

dfs的简单应用

#include<cstdio>
int n,m;
char grid[105][105];//存储网格；
int dir[8][2]={{-1,-1},{-1,0},{-1,1},{0,1},{0,-1},{1,1},{1,0},{1,-1}};
void DFS(int x,int y)//从(x,y)位置进行DFS
{
    int i,xx,yy;
    grid[x][y]='*';//进过后设置成*保证不会在经过了
    for(i=0;i<8;i++)
    {
        xx=x+dir[i][0];
        yy=y+dir[i][1];
        if(xx>=n||yy>=m||xx<0||yy<0)//判断
        continue;
        if(grid[xx][yy]!='*')
        DFS(xx,yy);
    }
}
int main()
{
    int i,j;
    int count;//统计数目
    while(scanf("%d%d",&n,&m),n)
    {
        for(i=0;i<n;i++)
        {
            scanf("%s",grid[i]);
        }
        count=0;
        for(i=0;i<n;i++)
        {
            for(j=0;j<m;j++)
            {
                if(grid[i][j]=='@')
                {
                    DFS(i,j);//从(i,j)位置进行DFS；
                    count++;
                }
            }
        }
        printf("%d\n",count);
    }
    return 0;
}