https://www.luogu.com.cn/problem/P1141

#include <bits/stdc++.h>
using namespace std;
int n, m;
int dx[4]={0,0,-1,1};
int dy[4]={-1,1,0,0};
char s[1005][1005];
int ans = 0,vis[1005][1005];
void dfs(int x,int y){
	ans++;	
	for(int i=0;i<=3;i++){
		int nx=x+dx[i],ny=y+dy[i];
		if(nx<=n&&nx>=1&&ny<=n&&ny>=1&&s[nx][ny]!=s[x][y]&&!vis[nx][ny]){
			vis[nx][ny]=1;
			dfs(nx,ny);
		}
	}
}
int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            cin >> s[i][j];
        }
    }

    for (int i = 1; i <= m; i++) {
    	memset(vis,0,sizeof(vis));
        ans = 0;
        int x, y;
        cin >> x >> y;
        vis[x][y]=1;
        dfs(x, y);
        cout << ans << endl;
    }

    return 0;
}