0分RE，思路样例感觉都没问题

大佬求调

#include <iostream>
#include <queue>
#include <algorithm>
#include <cstring>
using namespace std;

typedef pair<int, int> PII;
const int N = 1010;
int n, m;
int c[N][N];
int h[N][N];
int ans[100010];
int dx[] = {-1, 0, 1, 0};
int dy[] = {0, 1, 0, -1};

int bfs(int sx, int sy, int k)
{
    int sum = 1;
    queue<PII> q;
    q.push({sx, sy});
    h[sx][sy] = k;
    while (q.size())
    {
        PII t = q.front();
        q.pop();
        for (int i = 0; i < 4; ++i)
        {
            int x = t.first + dx[i];
            int y = t.second + dy[i];
            if (x >= 1 && x <= n && y >= 1 && y <= n && c[x][y] + c[t.first][t.second] == 1 && !h[x][y])
            {
//              if (ans[x][y]) return ans[x][y];
                sum++;
                h[x][y] = k;
                q.push({x, y});
            }
        }
    }
    ans[k] = sum;
}

int main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; ++i)
    {
        for (int j = 1; j <= n; ++j)
        {
            char s;
            cin >> s;
            if (s == '0') c[i][j] = 0;
            else c[i][j] = 1;
        }
    }
    for (int i = 1; i <= m; ++i) 
    {
        int x, y;
        cin >> x >> y;
        if (h[x][y])
        {
            cout << ans[h[x][y]] << endl;
        }
        else
        {
            bfs(x, y, i);
            cout << ans[i] << endl; 
        }
    }
}