连通块问题

#include<bits/stdc++.h>
using namespace std;

int vis[105][105],dx[8] = {1,-1,0,0,1,1,-1,-1},dy[8] = {0,0,1,-1,1,-1,1,-1},n,m;
char a[105][105];

void DFS(int x,int y){
    vis[x][y] = 1;
    for(int i = 0;i < 8;i ++){
        int nx = x + dx[i];
        int ny = y + dy[i];
        if(nx >= 0 and ny >= 0 and nx < n and ny < m and vis[nx][ny] == 0 and a[nx][ny] == 'W'){
            vis[nx][ny] = 1;
            DFS(nx,ny);
        }
    }
}

int main(){
    cin >> n >> m;
    for(int i = 0;i < n;i ++){
        for(int j = 0;j < m;j ++){
            cin >> a[i][j];
        }
    }
    int ans = 0;
    for(int i = 0;i < n;i ++){
        for(int j = 0;j < m;j ++){
            if(vis[i][j] == 0 and a[i][j] == 'W'){
                ans ++;
                DFS(i,j);
            }
        }
    }
    cout << ans;
    return 0;
}