Compilare: main.cpp: In function 'long long int calcSum(std::vector<std::vector<int> >)': main.cpp:7:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < x.size(); ++i) { ~~^~~~~~~~~~ main.cpp:8:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < x[i].size(); ++j) ~~^~~~~~~~~~~~~ main.cpp: In function 'void reverseLine(std::vector<std::vector<int> >&, int)': main.cpp:14:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < x[line].size(); ++j) ~~^~~~~~~~~~~~~~~~ main.cpp: In function 'void reverseCol(std::vector<std::vector<int> >&, int)': main.cpp:18:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < x.size(); ++i) ~~^~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:23:35: 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:24:37: 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); ^