Compilare: user.cpp: In function ‘int main()’: user.cpp:35:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < left.size(); i++) ^ user.cpp:11:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("swaps2.in", "r", stdin); ^ user.cpp:12:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("swaps2.out", "w", stdout); ^ user.cpp:14:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); getchar(); ^