problem involving matrix & binary search tree

Question

Hi,i am a new guy on this forum.I have only recently
taken to C# programming and facing a few problems.I hope

to get some help here and get to know some people.

My present problem looks like this:-

           
I have a 5x5 Matrix. Each cell consists a string value

ex: URL of any website.
 
I want to find out which string value occurs( i.e.

repeats ) maximum no. of times in the matrix.

 I have a hint that BINARY SEARCH TREE will be used here

and that NODE class in c# may be used to implement

trees.
 
The output can be in the form of array/matrix/Binary

Search Tree etc.

I am not allowed to use unsafe block to create/access

trees.