题目描述
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.
由于近期的降雨，雨水汇集在农民约翰的田地不同的地方。我们用一个NxM(1<=N<=100;1<=M<=100)网格图表示。每个网格中有水('W') 或是旱地('.')。一个网格与其周围的八个网格相连，而一组相连的网格视为一个水坑。约翰想弄清楚他的田地已经形成了多少水坑。给出约翰田地的示意图，确定当中有多少水坑。
输入格式
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.
第1行：两个空格隔开的整数：N 和 M 第2行到第N+1行：每行M个字符，每个字符是'W'或'.'，它们表示网格图中的一排。字符之间没有空格。
输出格式
Line 1: The number of ponds in Farmer John's field.
一行：水坑的数量
输入输出样例
输入
10 12 W........WW. .WWW.....WWW ....WW...WW. .........WW. .........W.. ..W......W.. .W.W.....WW. W.W.W.....W. .W.W......W. ..W.......W.
输出
3
说明/提示
OUTPUT DETAILS: There are three ponds: one in the upper left, one in the lower left, and one along the right side.
import java.util.*;
// 1:无需package
// 2: 类名必须Main, 不可修改public class Main {static int n,m;public static void main(String[] args) {Scanner sc = new Scanner(System.in);n = sc.nextInt();m = sc.nextInt();char[][] map = new char[n][m];for(int i = 0;i<n;i++){map[i] = sc.next().toCharArray();}int ans = 0;for(int i =0;i<n;i++){for(int j =0;j<m;j++){if(map[i][j] == 'W'){ans++;dfs(map,i,j);}}}System.out.println(ans);}public static void dfs(char[][]map,int x,int y){map[x][y] = '.';for(int i =-1;i<=1;i++){for(int j =-1;j<=1;j++){if(i==0 && j == 0)continue;int nextX = i+x,nextY = j+y;if(nextX<0 || nextX>=n || nextY<0 || nextY>=m || map[nextX][nextY] == '.')continue;dfs(map,nextX,nextY);}}}
}