music

# tree lookup

## summary

This subchapter looks at tree lookup.

## free computer programming text book project

If you like the idea of this project,

### stub section

This subchapter is a stub section. It will be filled in with instructional material later. For now it serves the purpose of a place holder for the order of instruction.

Professors are invited to give feedback on both the proposed contents and the propsed order of this text book. Send commentary to Milo, PO Box 1361, Tustin, California, 92781, USA.

# tree lookup

This subchapter looks at tree lookup.

## Stanford introduction

This [the following section until marked as end of Stanford University items] is article #110 in the Stanford CS Education Library. This and other free CS materials are available at the library (http://cslibrary.stanford.edu/). That people seeking education should have the opportunity to find it. This article may be used, reproduced, excerpted, or sold so long as this paragraph is clearly reproduced. Copyright 2000-2001, Nick Parlante, nick.parlante@cs.stanford.edu. [Stanford items are marked by a very light Stanford cardinal background.]

### Typical Binary Tree Code in C/C++

{NOTE; the original Stanford document separated the C/C++ and the Java discusssions. The material is interwoven here because this book uses the approach of teaching abasic concept and then showing it in multiple languages.]

As an introduction, we’ll look at the code for the two most basic binary search tree operations -- lookup() and insert(). The code here works for C or C++. Java programers can read the discussion here, and then look at the Java versions.

In C or C++, the binary tree is built with a node type like this…

struct node {
int data;
struct node* left;
struct node* right;

}

### lokkup()

Given a binary search tree and a “target” value, search the tree to see if it contains the target. The basic pattern of the lookup() code occurs in many recursive tree algorithms: deal with the base case where the tree is empty, deal with the current node, and then use recursion to deal with the subtrees. If the tree is a binary search tree, there is often some sort of less-than test on the node to decide if the recursion should go left or right.

/*
Given a binary tree, return true if a node
with the target data is found in the tree. Recurs
down the tree, chooses the left or right
branch by comparing the target to each node.
*/
static int lookup(struct node* node, int target) {
// 1. Base case == empty tree
// in that case, the target is not found so return false
if (node == NULL) {
return(false);
}
else {
// 2. see if found here
if (target == node->data) return(true);
else {
// 3. otherwise recur down the correct subtree
if (target < node->data) return(lookup(node->left, target));
else return(lookup(node->right, target)); }
}
}
}

The lookup() algorithm could be written as a while-loop that iterates down the tree. Our version uses recursion to help prepare you for the problems below that require recursion.

This [the quoted passages above] is article #110 in the Stanford CS Education Library. This and other free CS materials are available at the library (http://cslibrary.stanford.edu/). That people seeking education should have the opportunity to find it. This article may be used, reproduced, excerpted, or sold so long as this paragraph is clearly reproduced. Copyright 2000-2001, Nick Parlante, nick.parlante@cs.stanford.edu. [Stanford items are marked by a very light Stanford cardinal background.]

{NOTE; the original Stanford document separated the C/C++ and the Java discusssions. The material is interwoven here because this book uses the approach of teaching abasic concept and then showing it in multiple languages.]

# free music player coding example

Coding example: I am making heavily documented and explained open source code for a method to play music for free — almost any song, no subscription fees, no download costs, no advertisements, all completely legal. This is done by building a front-end to YouTube (which checks the copyright permissions for you).

View music player in action: www.musicinpublic.com/.

Create your own copy from the original source code/ (presented for learning programming).

## view text bookHTML file

Because I no longer have the computer and software to make PDFs, the book is available as an HTML file, which you can convert into a PDF.

 previous page next page
 Tweets by @osdata

## free computer programming text book project

Building a free downloadable text book on computer programming for university, college, community college, and high school classes in computer programming.

If you like the idea of this project,

send donations to:
Milo
PO Box 1361
Tustin, California 92781

Supporting the entire project:

If you have a business or organization that can support the entire cost of this project, please contact Pr Ntr Kmt (my church)

Some or all of the material on this web page appears in the

This web site handcrafted on Macintosh computers using Tom Bender’s Tex-Edit Plus and served using FreeBSD .

†UNIX used as a generic term unless specifically used as a trademark (such as in the phrase “UNIX certified”). UNIX is a registered trademark in the United States and other countries, licensed exclusively through X/Open Company Ltd.

Names and logos of various OSs are trademarks of their respective owners.