Hello , i was having trouble understanding uva 11080 Place The Guards.

My idea is that if each the connected components is of the form NODE-->NODE-->NODE-->... and so on , and the number of nodes are even then it is possible to place the guards , but this seems to be giving me WA .

Also this question was tagged under bipartite graph check , so if someone could explain that angle of looking into it too , it will be appreciated ,

thanks