BFS记忆化代码，70分，4个TLE(包括测试点1）

#include<iostream>
#include<queue>
#include<vector>
#include<climits>
using namespace std;
int px[5]{0,0,0,-1,1};
int py[5]{0,1,-1,0,0};
struct node{
    int x,y;
};
int n,m;
int maxn;
vector<vector<char> >op;
vector<vector<bool> >vis;
vector<vector<int> >jiyi;
queue<node>q;
void bfs(node t1){
    q.push(t1);
    node t;
    maxn=0;
    vis[t1.x][t1.y]=true;
    maxn++;
    while(!q.empty()){
        t=q.front();
        q.pop();
        node p;
        for(int i=1;i<=4;i++){
            p.x=t.x+px[i];
            p.y=t.y+py[i];
            if(p.x>=1&&p.x<=n&&p.y>=1&&p.y<=n&&op[p.x][p.y]!=op[t.x][t.y]&&vis[p.x][p.y]==false){
                //cout<<p.x<<" "<<p.y<<endl;

                maxn++;
                vis[p.x][p.y]=true;
                q.push(p);
            }
        }

    }
    jiyi[t1.x][t1.y]=maxn;
    cout<<maxn<<endl;
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
    cin>>n>>m;
    node t;
    op.assign(n+5,vector<char>(n+5,'.'));
    jiyi.assign(n+5,vector<int>(n+5,0));
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            cin>>op[i][j];
        }
    }
    for(int i=1;i<=m;i++){
        vis.assign(n+5,vector<bool>(n+5,false));
        cin>>t.x>>t.y;
        if(jiyi[t.x][t.y]){
            cout<<jiyi[t.x][t.y]<<endl;
            continue;
        }
        bfs(t);
    }
    return 0;
}