datastructures presentation

8/9/2019 DataStructures Presentation

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Introduction to Data Structures


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Data Structures

A data structure is a scheme

for organizing data in the

memory of a computer.

Some of the more commonly

used data structures include

lists, arrays, stacks, queues,

heaps, trees, and graphs.Binary Tree


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"#ample$ A %ueue

A queue is an e#ample of commonly used simple datastructure. A queue has !eginning and end, called the front

and back of the queue.

Data enters the queue at one end and lea&es at the other.

Because of this, data e#its the queue in the same order in

which it enters the queue, like people in a checkout line at

a supermarket.


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"#ample$ A Binary Tree

A binary tree is another

commonly used data

structure. It is organized like

an upside down tree.

"ach spot on the tree, called

a node, holds an item of data

along with a left pointer anda right pointer. Binary Tree


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"#ample$ A Binary Tree

The pointers are lined up

so that the structure forms

the upside down tree, with

a single node at the top,called the root node, and

!ranches increasing on the

left and right as you go

down the tree.Binary Tree


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hoosing Data Structures

By comparing the queue with

the !inary tree, you can see

how the structure of the data

affects what can !e done

efficiently with the data.


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A queue is a good data structure

to use for storing things that need

to !e kept in order, such as a set

of documents waiting to !e

printed on a network printer.

.


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A !inary tree is a good data

structure to use for searching

sorted data.

The middle item from the list isstored in the root node, with

lesser items to the left and greater

items to the right.


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A search !egins at the root. The

computer either find the data, or

mo&es left or right, depending on

the &alue for which you are

searching.

"ach mo&e down the tree cuts the

remaining data in half.


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Items can !e located &ery quicklyin a tree.

Telephone directory assistanceinformation is stored in a tree, sothat a name and phone num!ercan !e found quickly.


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)or some applications, a queue isthe !est data structure to use.

)or others, a !inary tree is !etter.

*rogrammers choose fromamong many data structures!ased on how the data will !eused !y the program.


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Data Structures in Alice

Alice has two !uilt+in data structures

that can !e used to organize data, or

to create other data structures$

-ists

Arrays


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-ists

A list is an ordered set of data. It is often used to store

o!'ects that are to !e processed sequentially.

A list can !e used

to create a queue.


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Arrays

An array is an inde#ed set of &aria!les, such as

dancer /0, dancer 10, dancer 20,3 It is like a set of

!o#es that hold things.

A list is a set of items.

An array is a set of

&aria!les that each

store an item.


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Arrays and -ists

4ou can see the difference !etween arrays and

lists when you delete items.


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Arrays and -ists

In a list, the missing spot is filled in when

something is deleted.


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Arrays and -ists

In an array, an empty &aria!le is left !ehind

when something is deleted.


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-ists

A list is created in Alice !y checking the make a

list !o# when creating a new &aria!le.

Make a list !o#


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-ists

The For all in order and For all together tiles can

!e used to work with lists. They are at the

!ottom of the editor area.


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Arrays

Arrays can !e created in a similar manner, !ut

more often they are created using the array

&isualization o!'ect from the Alice local gallery.

The Array 5isualization o!'ect

has special properties and

methods for manipulatingthe elements in an array.


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Arrays

Alice has a set of !uilt+in functions that can !e

performed on arrays.

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