What's the meaning of the "return" here?

[meiyantao]

This codeblock comes from Mr Weiss's book "Data Sturucture and Algorithm Analysis in C++"(Third Edition). I have some questions about it.

/**
*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);
}

My questions have put in the codeblock.I know that my English is bad,if you find some errors in my English syntax,please help me too! As you know,it's impossible to study C++ well without English.
Thanks ^_^

[WaltP]

This codeblock comes from Mr Weiss's book "Data Sturucture and Algorithm Analysis in C++"(Third Edition). I have some questions about it.

First of all, please format your code so it can be followed. I'll format it as I go...

/**
*  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);
    }
}

So here's a simplified version of the function.

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; 
}

[meiyantao]

Thank you very much!

[Ancient Dragon]

As you know,it's impossible to study C++ well without English.
Thanks ^_^

Probably because English has become the universal language of business. Anyone who needs to conduct business in todays global world needs to know English.

And the English you posted looks great to me. :)

[meiyantao]

So here's a simplified version of the function.

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; 
}

Yes,thank you.It's beautiful.Your code is most the same as Mr Weiss's. Ha,I am trying to implement all of his book,but I can't write them without looking his code.

[Narue]

I'm most certainly not a fan of Weiss' code, but the book you have is half decent in terms of coverage. His stuff is noticeably dumbed down, but if you want to take your trees to the next level, try this.

[meiyantao]

I'm most certainly not a fan of Weiss' code, but the book you have is half decent in terms of coverage. His stuff is noticeably dumbed down, but if you want to take your trees to the next level, try this.

I will try to do it,thank you very much!

[ss339]

Probably because English has become the universal language of business. Anyone who needs to conduct business in todays global world needs to know English.

Thats the problem man....

Many people that dont have english as first language, it is much harder...

I know this first hand..

[WolfPack]

! As you know,it's impossible to study C++ well without English.

If you have good C++ books written in or translated to a language you understand, English is not a necessity. Ask any Japanese C++ programmer. You will find it hard communicating in an English IT forum like this, but you can learn C++ without English.