Compilare: user.cpp: In function ‘int main()’: user.cpp:17:24: warning: unused variable ‘j’ [-Wunused-variable] int N, M, K, Q, i, j, x, y; ^ user.cpp: In function ‘void init(std::vector<std::vector<int> >&)’: user.cpp:100:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < matrix.size(); i++) ^ user.cpp:101:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < matrix[i].size(); j++) ^