POJ_2386 Lake Counting （dfs 错了一个负号找了一上午）

import java.util.Scanner;

public class Main{
    int n,m;
    static int N = 105, M =105;
    static char field[][] = new char[N][M];
    static int res = 0;
    
    static void dfs(int x, int y) {
        field[x][y] = ‘.‘;
        for(int dx=-1;dx<=1;dx++)
            for(int dy=-1;dy<=1;dy++)
            {
                int nx=x+dx;
                int ny=y+dy;
                if(nx>=0&&nx<N&&ny>=0&&ny<M&&(field[nx][ny]==‘W‘))
                dfs(nx,ny);
            }
        
        return;
    }
    
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        N=cin.nextInt();
        M=cin.nextInt();
        String s;
        for(int i=0;i<N;i++){
            s = cin.next();
            for(int j=0;j<M;j++)
                field[i][j]=s.charAt(j);
        }
        

        
        for(int i=0;i<N;i++){
            for(int j=0;j<M;j++){
                if(field[i][j]==‘W‘){
                    dfs(i,j);    
                    res++;
                }
            }
        }    
        System.out.println(res);
        cin.close();
    }
}