为什么有WA和TLE，调了好久...

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<queue>
using namespace std;
int n;
int m;
int dp[1001][1001];
int migong[1001][1001];
struct node{
    int x,y;
    node operator+ (const node S)const{
        node ans={x+S.x,y+S.y};
        return ans;
    }
};
node fangxiang[5]={{0,0},{0,-1},{0,1},{1,0},{-1,0}};
int bfs(int x,int y){
    queue<node> q;
    queue<node> ue;
    q.push({x,y});
    int ans=0;
    bool went[n+1][n+1]={};
    while(!q.empty()){
        node now=q.front();
        q.pop();
        ue.push(now);
        for(int i=1;i<=4;i++){
            node will=now+fangxiang[i];
            if(will.x>0 && will.x<=n && will.y>0 && will.y<=n && migong[will.x][will.y]==!migong[now.x][now.y] && !went[will.x][will.y]){
                ans++;
                q.push(will);
                went[will.x][will.y]=1;
            }
        }
    }
    //cout<<ans<<endl;
    while(ue.size()){
        node now1=ue.front();
        ue.pop();
        dp[now1.x][now1.y]=ans;
    }
    return dp[x][y];
}
int main(){
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            scanf("%1d",&migong[i][j]);
        }
    }
    for(int i=1;i<=m;i++){
        int a,b;
        cin>>a>>b;
        if(dp[a][b]){
            cout<<dp[a][b]<<endl;
            continue;
        }
        cout<<bfs(a,b)<<endl;
    }
    return 0;
}