Compilare: user.cpp: In function ‘void DFS(int)’: user.cpp:31:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<a[x].size(); ++i) ^ user.cpp: In function ‘void solve()’: user.cpp:68:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<sol.size()-1; ++i) ^