poj 2386 Lake Counting

Lake Counting

Time Limit: 1000MS Memory Limit: 65536KTotal Submissions: 16497 Accepted: 8356

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

Sample Output

3

这道题是dfs（我是新手），对所有点进行遍历，如果是w则进行dfs，在dfs过程中将关联的w改为'  .   '（平地）；

#include<iostream>using namespace std;#define MAX 102char aa[MAX][MAX];int m,n;void dfs(int x,int y){aa[x][y]='.';for(int dx=-1;dx<=1;dx++){for(int dy=-1;dy<=1;dy++){int nx=x+dx,ny=y+dy;if(0<=nx && nx<m && 0<=ny && ny<n && aa[nx][ny]=='W')dfs(nx,ny);}}}int main(){cin>>m>>n;for(int i=0;i<m;i++)for(int j=0;j<n;j++)cin>>aa[i][j];int res=0;for(int i=0;i<m;i++){for(int j=0;j<n;j++){if(aa[i][j]=='W'){dfs(i,j);res++;}}}cout<<res<<endl;return 0;}