function IsItABinarySearchTree(t:BinaryTree): TAnswer;
// the data type that is received
// has a binary tree struct.
// ie t^.data is root
// t^.left.data is left sub tree node
// t^.right.data is right sub tree node
// for a binary search tree values must be smallest on sub tree nodes on LEFT
var ans: TAnswer;
arr : array of integer;
begin (* each node from left <= right node *)
ans.known := true; (* set to true *)
arr := nil; // like to declare incase of random values!
// no need for root node to check this, i to make sure the trees keep the
arr[0] := t^.data; //root not needed for this one
arr[1] := t^.left.data;
arr[2] := t^.right.data;
arr[3] := t^.left.left.data;
arr[4] := t^.left.right.data;
arr[5] := t^.right.left.data;
arr[6] := t^.right.right.data;
// check if left values are smaller to right
// if they are all in order from left to right then OK
if ((arr[1] <= arr[2]) AND (arr[3] <= arr[4]) AND
(arr[4] <= arr[5]) AND (arr[5] <= arr[6])) then
begin
ans.answer := TRUE;
ans.feedback := 'It Is A ...';
end
else begin
ans.answer := FALSE;
ans.feedback := 'It is not A';
end;
IsItABinarySearchTree := ans; (*return this*)
end;