data representation through list in python.

1. Data Representation Methods
By
Saif Ur Rehman

2. Agenda
 Linear List Array Representation
 Right To Left Mapping
 Left To Right Mapping
 Mapping that Skip every Other Position
 Wrap Around Mapping
 Adding and Removing Elements from Array List
 Data Type of Array List Elements

3. Linear List Array Representation
 Also called one dimensional array.
 We can create an empty list array using the square bracket [].
A =
0 1 2 3 4 5
 Can access each and every element of an array using its index.
 For example A[i]. It gives an element an element of A depending upon the
value of i.
a b c d e f

4. Right To Left Mapping
 The concept of mapping in Data Structure is much similar to that of
Mathematics.
 Mapping is associating each element into the array indexes.
 In right to left mapping we associate elements into the linear list from right
towards left as shown below.
 This mapping is implemented through the following python code.
List=[]
for i in range(5)
List.append(len(List)-1,value)
e d c b a

5. Left To Right Mapping
 This mapping is frequently used because it is easy to implement in which
elements are mapped from left through right of the array list.
 It is very efficient method which let to the designing of many important
algorithms, which are challenging without it.
 For instance we have some data elements which we want to map to the array list
as shown.
Code for implementation
List = []
for i in range(5)
List.append(elements)
q w r t y

6. Mapping that skips
Every Other Position
 As mention above, in this mapping we skip every other position as per our requirement as
shown below.
Let’s implement it with following code.
LisT = []
for iterate in range(7)
elements =input(“enter values “)
If iterate%2 ==1
LisT.append(elements)
Else
continue
a b c d

7. Wrap Around Mapping
 As the name shows in this mapping we assign the data elements from both the
ends of the array list as shown in the figure below.
 This mapping is rarely used because of it it’s complex structure which makes
it difficult to implement.
 The other problem with this mapping is the issue of time. This mapping takes
much more time than the other two mapping.
d e a b c

8. Adding an element in Array List
 To add element we must physically relocate elements that are to the right of
the newly inserted element. We must also increment size by 1.
 For example we have an array which has some elements as shown and we
have to add ‘g’ in index 1.
Size = 5
add(1,’g’)
Size = 6
a b c d e
a g b c d e

9. Removing an element from Array List
 To remove an element we must move elements to the right of removed element
left by 1 and reduce size by 1.let us assume that we have a filled array list and we
want to remove the element at index 3.
 A =
0 1 2 3 4
size = 5
A[3] = []
now A becomes
0 1 2 3
size = 4
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square rectangle ellipse oval

10. Data type of Array List elements
 Data type of list elements are unknown. They are considered as class of type
list.
 We cannot put elements of primitive data types (int,float,char,double, etc)
into our linear list.

11. Thank You