Hello everyone,
I have seen many problems which can be solved using tree center.
So, I would like to know about it.
If someone can provide resources or explain it here in comments, It would be great!

and also my approach for today atCoder Problem C was something like this : ( failed! )

• Find an extreme of a diamemter of tree, This can be done by running a dfs from any arbitrary node. The node whose depth is highest is one of the extreme. ( Please correct me? )
• find the diameter from this extreme ( the highest depth from this node ).
• the nodes with the depth equal to the diameter are pushed into a vector ( let's say A ).
• Now, for every node in the vector A, Run a dfs and count the no of nodes having depth greater than K. the minimum of these would be the answer.

Where did I go wrong?
Someone please help me?

Thanks in Advance