Compilare: main.cpp: In function 'void zigsort()': main.cpp:40:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (long long i = 0; i < a.size() - 1; i++) { ~~^~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:53:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("zigsort.in", "r", stdin); ^ main.cpp:54:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("zigsort.out", "w", stdout); ^