题目

#include <bits/stdc++.h>
#define LL long long
#define DB double
#define BUG cout << "OoO" << endl

using namespace std;

const int N = 1001, Max_N = 1000001;
int n, m, ax, ay;
int d, mp[N][N], vis[N][N], ans[Max_N];
int dx[] = {0, 0, -1, 1}, dy[] = {-1, 1, 0, 0};
struct Node {int x, y;};


int BFS(int ax, int ay, int d)
{
	int ret = 1;
	queue <Node> q; 
	q.push(Node{ax, ay});
	vis[ax][ay] = 1;
	
	while(!q.empty())
	{
		Node u = q.front();
		q.pop();
		
		for(int i = 0; i < 4; i ++ )
		{
			int xx = u.x + dx[i];
			int yy = u.y + dy[i];
			
			if(mp[u.x][u.y] == mp[xx][yy]) continue;
			if(vis[xx][yy] > 0) continue;
			if(xx < 1 || xx > n || yy < 1 || yy > n) continue;
			
			q.push(Node{xx, yy});
			ret ++ ;
			vis[xx][yy] = d;
		}
	}
	
	return ret;
}

int main()
{
	scanf("%d%d", &n, &m);
	
	for(int i = 1; i <= n; i ++ )
	{
		for(int j = 1; j <= n; j ++ )
		{
			char ch;
			cin >> ch;
			mp[i][j] = ch - '0';
		}
	}
	
	memset(vis, 0, sizeof vis);
	for(int i = 0; i < m; i ++ )
	{	
		scanf("%d%d", &ax, &ay);
		
		if(vis[ax][ay] == 0)
		{
			d ++ ;
			ans[d] = BFS(ax, ay, d);
		}
		
		printf("%d\n", ans[vis[ax][ay]]);
	}
	
    return 0;
}

为什么不是RE就是WA啊！