基础的BFS，把STL的队列改成手写队列了，搜索结果也另外存储了，不知道还能怎么优化

#include <bits/stdc++.h>
using namespace std;
int n,m,ans;
int mp[1005][1005],a[1005][1005];
bool vis[1005][1005];
int l,r;
struct node {
	int x,y;
}q[1000004];
int dx[5] = {0,1,-1,0,0},dy[5]= {0,0,0,-1,1};
inline void bfs(int x,int y) {
	++ans;
	vis[x][y] = true;
	q[r++] = node{x,y};
	while(!(l == r)) {
		node t = q[l];
		++l;
		for (int i = 1; i <= 4; i++) {
			int tx =t.x +dx[i],ty = t.y+dy[i];
			if (tx < 1 || ty < 1 || tx > n || ty > n) continue;
			if (mp[tx][ty] == mp[t.x][t.y]) continue;
			if (vis[tx][ty]) continue;
			vis[tx][ty] = true;
			if (a[tx][ty] != 0) {
				ans += a[tx][ty];
				continue;
			}
			++ans;
			q[r++] = node{tx,ty};
		}
	}
}
int main () {
	cin >> n >> m;
	for (int i = 1; i <= n ;i++) {
		for (int j = 1; j <= n; j++) {
			char c;
			cin >> c;
			mp[i][j] =c - '0';
		}
	}
	
	while (m--) {
		int x,y;
		cin >> x >> y;
		if (a[x][y] != 0 ) {
			cout << a[x][y] << endl;
			continue;
		}
		ans = 0;
		memset(vis,0,sizeof(vis));
		memset(q,0,sizeof(q));
		l = 0,r = 0;
		bfs(x,y);
		for (int i = 0; i <= r; i++) {
			if (a[q[i].x][q[i].y] == 0) a[q[i].x][q[i].y] = ans;
		}
		cout << ans << endl;
	}
	return 0;
}