classSolution {public: vector<vector<int>> multiply(vector<vector<int>>& A, vector<vector<int>>&B) { vector<vector<int>>ret;intha =A.size();if(!ha)returnret;intwa = A[0].size();if(!wa)returnret;inthb =wa;intwb = B[0].size();if(!wb)returnret;//Preprocessingunordered_map<...