Compilare: user.cpp: In function ‘void dfs(int, int)’: user.cpp:14:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<v[s].size();++i) ^ user.cpp: In function ‘bool valid(int)’: user.cpp:23:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (p.count()!=n) return false; ^ user.cpp:20:9: warning: unused variable ‘i’ [-Wunused-variable] int i; ^