Compilare: main.cpp: In function 'void reverseLine(std::vector<std::vector<int> >&, int)': main.cpp:17:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < x[line].size(); ++j) ~~^~~~~~~~~~~~~~~~ main.cpp:16:9: warning: unused variable 'length' [-Wunused-variable] int length = x[line].size(); ^~~~~~ main.cpp: In function 'void reverseCol(std::vector<std::vector<int> >&, int)': main.cpp:22:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < x.size(); ++i) ~~^~~~~~~~~~ main.cpp:21:9: warning: unused variable 'length' [-Wunused-variable] int length = x.size(); ^~~~~~ main.cpp: In function 'int main()': main.cpp:27:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("flip.in", "r", stdin); ^ main.cpp:28:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("flip.out", "w", stdout); ^