The document discusses various methods for representing data in arrays, including: - Linear (one-dimensional) array representation with indexing to access elements - Right to left and left to right mapping of elements to array positions - Mapping that skips every other array position - Wrap around mapping that assigns elements to both ends of the array It also covers adding and removing elements from array lists, including needing to relocate other elements, and that array list elements can be of any data type rather than just primitive types.

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