Compilare: main.cpp: In function 'void buildLevel(int)': main.cpp:29:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < cells[lvl].size(); i++){ ~~^~~~~~~~~~~~~~~~~~~ main.cpp: In function 'void setIO(std::__cxx11::string, bool, bool)': main.cpp:7:50: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] if(input) freopen(inputname.c_str(), "r", stdin); ^ main.cpp:8:53: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] if(output) freopen(outputname.c_str(), "w", stdout); ^ main.cpp: In function 'int main()': main.cpp:75:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &m); ^ main.cpp:78:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &a[i][j]); ^