《挑战》2.1 POJ 2386 Lake Counting (简单的dfs) 

 1 # include<cstdio>
 2 # include<iostream>
 3 
 4 using namespace std;
 5 
 6 # define MAX 123
 7 
 8 char grid[MAX][MAX];
 9 int nxt[8][2] = { {1,0},{0,-1},{-1,0},{0,1},{1,1},{1,-1},{-1,1},{-1,-1} };
10 int n,m;
11 
12 int can_move( int x,int y )
13 {
14     if ( x>=0&&x<n&&y>=0&&y<m )
15     {
16         if ( grid[x][y]=='W' )
17             return 1;
18     }
19     return 0;
20 }
21 
22 
23 void dfs ( int x,int y )
24 {
25     grid[x][y] = '.';
26     for ( int i = 0;i < 8;i++ )
27     {
28         int n_x = x+nxt[i][0], n_y = y+nxt[i][1];
29         if ( can_move(n_x,n_y) )
30         {
31             dfs(n_x,n_y);
32         }
33     }
34     return;
35 }
36 
37 
38 int main(void)
39 {
40     //int n,m;
41     int res;
42     while ( scanf("%d%d",&n,&m)!=EOF )
43     {
44         res = 0;
45         for ( int i = 0;i < n;i++ )
46             scanf("%s",grid[i]);
47         for ( int i = 0;i < n;i++ )
48         {
49             for ( int j = 0;j < m;j++ )
50             {
51                 if ( grid[i][j]=='W' )
52                 {
53                     dfs(i,j);
54                     res++;
55                 }
56             }
57         }
58         printf("%d\n",res);
59     }
60 
61 
62     return 0;
63 }

 

A - Lake Counting

Description

Due to recent rains, water has pooled in various places in Farmer John's field, which is represented by a rectangle of N x M (1 <= N <= 100; 1 <= M <= 100) squares. Each square contains either water ('W') or dry land ('.'). Farmer John would like to figure out how many ponds have formed in his field. A pond is a connected set of squares with water in them, where a square is considered adjacent to all eight of its neighbors.        
Given a diagram of Farmer John's field, determine how many ponds he has.      

Input

       * Line 1: Two space-separated integers: N and M
* Lines 2..N+1: M characters per line representing one row of Farmer John's field. Each character is either 'W' or '.'. The characters do not have spaces between them.      

Output

       * Line 1: The number of ponds in Farmer John's field.      

Sample Input

10 12
W........WW.
.WWW.....WWW
....WW...WW.
.........WW.
.........W..
..W......W..
.W.W.....WW.
W.W.W.....W.
.W.W......W.
..W.......W.

Sample Output

3

Hint

OUTPUT DETAILS:        
There are three ponds: one in the upper left, one in the lower left,and one along the right side.

题目大意：

　　就是说一个n*m的网格中，求出联通块的个数。

解题思路：

　　就是一个dfs的基础题，从任意一个满足要求的点开始dfs，求出直到不能走动为止，res++。

复杂度：

　　O（8*m*n）

代码： 

posted @ 2015-07-25 00:08  BYYB_0506  阅读(181)  评论(0)  编辑  收藏  举报