/**
*This is a member function from the BinarySearchTree class.
*And It try to find whether there's a element equal to x in
*the binary search tree.
*/
bool BinarySearchTree::contains(const int & x, BinaryNode *t){
if(t==NULL)
return false;
/**
*Weiss put the following two sentences to the end of this 
*codeblock with an "else".But I think put it here can make 
*the code more readable.Is it an error?
*/
if(x == t->element)
return true; 
/**
*When I implemented these, I haven't added 
*"return" before recursive functions.
*Why must add "return" in the following sentences?
*How many times will the "return" really
*return when the promgram run?
*What will be happened,if I delete these "return"?
*/
if(x < t->element)
return contains(x,t->left); 
else if(t->element < x )
return contains(x,t->right);
}

/**
*  This is a member function from the BinarySearchTree class.
*  And It try to find whether there's a element equal to x in
*  the binary search tree.
*/
bool BinarySearchTree::contains(const int & x, BinaryNode *t)
{
    if (t == NULL)
    {
        return false;
 
    }
/**
* Weiss put the following two sentences to the end of this 
* codeblock with an "else".But I think put it here can make 
* the code more readable.Is it an error?
*/
    if (x == t->element)
    {
        return true; 
    }
//// The way the function is written, it doesn't seem to matter 
//// where this IF goes since each recursive call is part of a 
//// RETURN statement.
 
/**
*When I implemented these, I haven't added 
*"return" before recursive functions.
*Why must add "return" in the following sentences?
//// Because when the function finally gets to the end of 
//// the search, the value is passed back via the RETURN 
//// statements.  So the function returns the value, and 
//// upon returning returns the value again.  It just keeps 
//// passing  the value back to the previous recursion
 
*How many times will the "return" really
*return when the promgram run?
//// Exactly the same number of time the function is called...
 
*What will be happened,if I delete these "return"?
//// The function won't work.  Each return below actually 
//// calls the function again with the next node value to 
//// be tested.
*/
    if (x < t->element)
    {
        return contains(x,t->left); 
    }
    else 
    if (t->element < x )
    {
        return contains(x,t->right);
    }
}

bool BinarySearchTree::contains(const int & x, BinaryNode *t)
{
    if (t == NULL)
    {
        return false;
    }
 
    // if this element is before the one we're looking for, 
    //   call the function again with the next value (left)
    if (x < t->element)
    {
        return contains(x,t->left); 
    }
    // This element is not before the one we're looking for...
 
    // if this element is after the one we're looking for, 
    //   call the function again with the previous value (right)
    if (t->element < x )
    {
        return contains(x,t->right);
    }
    // This element is not before nor after.  Therefore it IS
    //    the one we're looking for.  We found it so return TRUE
    return true; 
}