我打算用 BFS，我 BFS 这块比较弱。但问什么 BFS 分数比 DFS 还低啊！

// Problem: 
//     P1141 01迷宫
//   
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/P1141
// Memory Limit: 128 MB
// Time Limit: 1000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

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

int n, m;
char ch[1005][1005];
bool vis[1005][1005];
int nex[4][2] = {
	{1, 0},
	{0, 1},
	{-1, 0},
	{0, -1}
};
int ans = 0;
struct point 
{
	int x;
	int y;
};
void bfs(int x, int y)
{
	queue<point> q;
	q.push(point{x, y});
	point data;
	while (!q.empty())
	{
		data = q.front();
		q.pop();
		for (int i = 0; i < 4; i++)
		{
			if (data.x + nex[i][0] <= n && data.y + nex[i][1] <= n
			&& data.x + nex[i][0] >= 1 && data.y + nex[i][1] >= 1)
			{
				if (ch[data.x][data.y] == '0'
				&& ch[data.x + nex[i][0]][data.y + nex[i][1]]
				== '1' && !vis[data.x + nex[i][0]][data.y + nex[i][1]])
				{
					ans++;
					q.push(point{
						data.x + nex[i][0],
						data.y + nex[i][1]
					});
					vis[data.x + nex[i][0]][data.y + nex[i][1]] = 1;
				}
				if (ch[data.x][data.y] == '1'
				&& ch[data.x + nex[i][0]][data.y + nex[i][1]]
				== '0'  && !vis[data.x + nex[i][0]][data.y + nex[i][1]])
				{
					ans++;
					q.push(point{
						data.x + nex[i][0],
						data.y + nex[i][1]
					});
					vis[data.x + nex[i][0]][data.y + nex[i][1]] = 1;
				} 
			}
			
		}
	}
}
int main()
{
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= n; j++)
		{
			cin >> ch[i][j];
		}
	}
	while (m--)
	{
		int x, y;
		cin >> x >> y;
		memset(vis, 0, sizeof(vis));
		ans = 0;
		bfs(x, y);
		cout << ans << endl;
	}
}