Hello,
I didn't understand the problem statement correctly. Do cities having power stations need to be connected to each other? The solution can be also having more than 1 connected components( Graphs ), right?

Edited by author 21.09.2017 09:28

Edited by author 21.09.2017 09:32

Questions you are asking are not about the statement
Questions you are asking are about the solution

The first question is maybe OK.
It is about the statement.
So there is "k cities have stations, the other cities need to be connected..."

Oh sorry, my bad!
However can you please help me ?
I will change the topic of the comment.

So we need to connect the other n-k cities

Oh, got it !
Thanks a lot :)

And second question is really about the solution

To understand it pay your attention to fact
That there is NO INFORMATION ABOUT ANY GRAPHS in the statement

No information about Graphs, you mean that whether it's directed or undirected?

Statement doesn't contain the word "graph"
So the graph is just a mathematical model used for solving such kind of problems
not something from statement
Also remember that it is ACM ICPC tradition to write informal statements
Statements which need to be formalized

Thanks a lot for helping me ! :)