Here's another coding exercise:
Convert a sorted list to binary search tree.
Note that the in order traversal of a binary search tree is a sorted list
The caveat is that we can only interpret a balanced binary search tree from the given list.
123456789

     5
  3       8
2  4    7  9
1       6

Node SortedListToBST(List<int> num, int start, int end, Node root)
{

int mid;

if ( (start + end) %2 == 0)
     mid = (start + end ) / 2 + 1;
else
    mid = (start + end) / 2

var node = new Node();
node.data = num[mid];

if (root != null)
if (num[mid] < root.data)
     root.left = node;
else
    root.right = node

node.left = SortedListToBST(num, start, mid-1, node);

node.right = SortedListToBST(num, mid + 1, end, node);

return node;

};