《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

Crawling in process... Crawling failed Time Limit:1000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u

Submit Status Practice POJ 2386

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：