Compilare: user.cpp: In function ‘bool valid(int, int)’: user.cpp:10:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = G[nod][0] ; i < G[nod].size() ; ++i ) ^ user.cpp: In function ‘void dfs(int)’: user.cpp:21:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = G[nod][0] ; i < G[nod].size() ; ++i ) ^