I'm having a problem with recursion.  I'm trying to create a function that will
return the number of interior nodes in a binary search tree (bst) not including
the root node.  The function below returns the number of interior nodes
including the root node but I can't figure out how to modify it so that it won't
include the root node.  Can anybody help me?  I would appreciate it a lot.

type
bst = ^bstnode;
bstnode = record
                number: integer;
                leftptr: bst;
                rightptr: bst;

{returns the number of interior nodes in the binary search tree not including
the root node}
  function interior(bst1: bst): integer;

  begin
    if bst1 = nil then
      interior := 0
    else if (bst1^.leftptr = nil) and (bst1^.rightptr = nil) then
      interior := 0
    else if (bst1^.leftptr <> nil) or (bst1^.rightptr <> nil) then
      interior := 1 + interior(bst1^.rightptr) + interior(bst1^.leftptr)
  end; {interior}

Like this :

result=interior(mybst);
if result>0 then Dec(result);

The only problem is that you have to do this externally, but you can always
make another function that contains just the code above.

In article <4rfdlc$...@canopus.cc.umanitoba.ca>,