Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:13:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[x].size();i++) ^ user.cpp: In function ‘bool check()’: user.cpp:20:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<vt[i].size();j++) ^ user.cpp: In function ‘int main()’: user.cpp:42:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<spec.size();i++) dfs(spec[i]); ^