Final Exam Review Spring 2004: Data structures


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Final Exam Review Spring 2004: Data structures

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Questions and Answers?

an array (17)is the pattern of bytes (each value called an element) in memory and is the most efficient way to store an ordered list of data items on a computer.
a matrix (40)is a two-dimensional array.
a tree (221)is a path that tells how to go from the root directory (base directory) to a specified file. It goes through a list of directories and subdirectories to where the file/item is located.
lists (218)are a type of structured text and sequences. Values in a list are called elements.
hash tables (256)/dictionaries/associate arrays are structures that can create rows for database tables, allowing us to relate keys and values but only in memory. Hash tables work well for database joins.

Karin Bowman

An array isn't a pattern. A directory structure is only one kind of tree. That definition of lists needs to be broader. Hash tables aren't necessarily about databases – that's just one use we put to them. Mark Guzdial

Is an array a collection of numbers in a specific sequence? In addition to what's mentioned above, lists can use methods such as sort() that strings cannot use.

An array doesn't have to contain numbers, but whatever things it does contain are numbered – i.e. referred to by number. (Is that what you mean by being 'in a specific sequence'?) Colin Potts

I know how to write examples to execute in the command area for trees, lists, and hash tables, but what about arrays and matrices? A little direction, please...

Hint: Sound samples are stored in arrays, and pixels are stored in matrices. Mark Guzdial

so then arrays are one-dimensional and matrices are two-dimensional?

Tres bien! Mark Guzdial

Do all these examples look ok?
For an Array:
samples = getSamples(sound)
print samples

For a Matrix:
pixel = getPixel(picture, 10,10)
print pixel

For a Tree:
filename= PickAFile()
print filename

For a List:
mylist = ["My", "name", "is", "Heather"]
print mylist

For a Hash table:
row = 'StudentName': 'Katie', 'StudentID': 'S1'
print row ['StudentName']

Heather Symon

For the array, could you show accessing an array element? Mark Guzdial

Mark, is this the tree you are looking for?
A tree is a hierarchical structure of files, functions or other kind of data into sub categories from the main/root element/function/directory.
Anu

lists: elements of any form, i.e, strings or numbers or pictures or sounds, are stored in sequence but not necessrily stored one after the other in the computer's memory. eg: ["alan",2,sound.wav,pic.jpg]

hash tables: to make rows of data in python by having indices of strings in an array.
array eg:
>>>hello="hello"
>>>print hello[2:4]
ll
ANu

Anu, your definition of tree is reasonable, and lists, too, but I don't get your definition of hash tables. Mark Guzdial

for an array:
>>>samples = getSamples(sound)
>>>print samples

is this correct??

print getSampleValueAt(sound,1)

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Sp2004 Final Exam Review last edited on 26 April 2004 at 3:49 pm by guzdial2.cc.gatech.edu