programming-for-dummies

382
Creating Trees
Figure 5-7:
A tree can
organize
names
alphabetically
by
last name.
A B • • • Z
Bally, David Burkins, John
To save the name David Bally, the computer stores the name under the B
node. To save the name John Burkins, the computer also stores this name
under the B node. To determine whether to store this new name before or
after any existing data, the computer examines the data and sorts it alphabetically.
In this way, the tree data structure not only stores data, but sorts
and organizes it as well.
If you had a long list of names stored in an array or a collection, finding a
name would require searching through the entire array or collection. However,
if that same list of names is stored in a tree, a name would be much
simpler to find because you’d only need to look at the first letter of a
person’s last name to find where it might be stored.
So if you want to find the name John Bally, start at the B node and ignore any
data stored under the other nodes. This makes searching and retrieving data
much faster than other types of data structures, which is why trees are so
commonly used in databases.
Binary trees
A variation of an ordered tree is a binary tree. Unlike an ordinary tree, every
node in a binary tree has at the most two nodes connected underneath. To
sort data, the left node contains values less than its parent node whereas the
right node contains values greater than its parent node, as shown in Figure 5-8.
By limiting each node to a maximum of two connected nodes, binary trees
make searching and sorting data fast and efficient.
10
Figure 5-8:
Binary trees
store and
sort data
by value.
4
8
9
11
12
19