Compilare: user.cpp: In function ‘int main()’: user.cpp:209:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < mat.size(); ++i) { ^ user.cpp:210:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < mat[i].size(); ++j) { ^ user.cpp:274:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < mat.size(); ++i) { ^ user.cpp:276:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < mat[i].size(); ++j) { ^ user.cpp:103:50: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen((fileInput + ".in").c_str(), "r", stdin); ^ user.cpp:104:52: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen((fileInput + ".out").c_str(), "w", stdout); ^