POJ 2386 Lake Counting

原题链接

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

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.

经典深搜

AC代码：

#include <iostream>using namespace std;int n,m;char f[100][101]; void dfs(int x,int y){    int i,j;    f[x][y]='.';    for(i=-1;i<=1;i++){        for(j=-1;j<=1;j++){            int dx=x+i;            int dy=y+j;            if(dx>=0 && dx<n && dy>=0 && dy<m && f[dx][dy]=='W')  dfs(dx,dy);        }    }    return;}int main(){    int i,j;    cin>>n>>m;    for(i=0;i<n;i++){        cin>>f[i];    }    int res=0;    for(i=0;i<n;i++){        for(j=0;j<m;j++){            if(f[i][j]=='W'){                dfs(i,j);                res++;            }        }    }    cout<<res<<endl;    return 0;}