Compilare: user.cpp: In function ‘bool check(int)’: user.cpp:32:13: warning: variable ‘a’ set but not used [-Wunused-but-set-variable] int a; ^ user.cpp:47:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < V.size(); i++) ^ user.cpp:76:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < X.size(); i++) ^ user.cpp:87:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < X.size(); i++) ^ user.cpp:94:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < X.size(); i++) ^ user.cpp:106:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < X.size(); i++) ^ user.cpp:112:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < X.size(); i++) ^