class Solution {
public:
   int largestOverlap(vector<vector<int>>& A, vector<vector<int>>& B) {
      int n = A.size();
      vector<int> pointsA, pointsB;
      for (int i = 0; i < n; ++i)
      {
         for (int j = 0; j < n; ++j)
         {
            if (A[i][j])pointsA.push_back(i * n + j);
            if (B[i][j])pointsB.push_back(i * n + j);
         }
      }
      unordered_map<string, int> dist;
      int res = 0;
      for (const auto& pA : pointsA)
      {
         for (const auto& pB : pointsB)
         {
            int xA = pA / n, yA = pA % n, xB = pB / n, yB = pB % n;
            string key = to_string(xA - xB) + ":" + to_string(yA - yB);
            ++dist[key];
            res = max(res, dist[key]);
         }
      }
      return res;
   }
};