Compilare: user.cpp: In function ‘bool check(int)’: user.cpp:83:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < V.size(); i++) ^ user.cpp:90:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < V.size(); i++) ^ user.cpp:102:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < V.size(); i++) ^ user.cpp:108:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < V.size(); i++) ^