Data -structures for class 12 , easy ppt

Computer Science
Chapter 5: Data-structures:
lists,stack,queue

Data-structures
It a way of organizing and storing data in such a manner so that it can be accessed
and work over it. This can be done efficiently and uses less resources are required. It
define the relationship between the data and the operations over those data. There
are various types of data structures defined that make it easier for the computer
programmer,to concentrate on the main problems rather than getting lost in the
details of data description and access.
Python Data Structure

List
It is a collections of items and each item has its own index value.
Index of first item is 0 and the last item is n-1.Here n is number of items in a list.
Indexing of list
Creating a list
Lists are enclosed in square brackets [ ] and each item is separated by a comma.
e.g.
list1 = [‘English', ‘Hindi', 1997, 2000];
list2 = [11, 22, 33, 44, 55 ];
list3 = ["a", "b", "c", "d"];
Data-structures

Access Items From A List
List items can be accessed using its index position.
output
e.g.
list =[3,5,9]
print(list[0])
print(list[1])
print(list[2])
print('Negativeindexing')
print(list[-1])
print(list[-2])
print(list[-3])
3
5
9
Negative indexing
9
5
3
Data-structures

Iterating Through A List
List elements can be accessed using looping statement.
e.g.
list =[3,5,9]
for i in range(0,len(list)):
print(list[i])
Output
3
5
9
Visit : python.mykvs.in for regular updates
Data-structures

Important methods and functions of List
Function
list.append()
list.extend()
list.insert()
list.remove()
del list[index]
list.clear()
list.pop()
list.index()
list.sort()
list.reverse()
len(list)
max(list)
min(list)
list(seq)
Description
Add an Item at end of a list
Add multiple Items at end of a list
insert an Item at a defined index
remove an Item from a list
Delete an Item from a list
empty all the list
Remove an Item at a defined index
Return index of first matched item
Sort the items of a list in ascending or descending order
Reverse the items of a list
Return total length of the list.
Return item with maximum value in the list.
Return item with min value in the list.
Converts a tuple, string, set, dictionary into
list.
Data-structures

Stack:
A stack is a linear data structure in which all the
insertion and deletion of data / values are done at one end only.





It is type of linear data structure.
It follows LIFO(Last In First Out)
property.
Insertion / Deletion in stack can
only be done from top.
Insertion in stack is also known as
a PUSH operation.
Deletion from stack is also known
as POP operation in stack.
Data-structures

Applications of Stack:
•
•
•
•
•
•
•
Expression Evaluation: It is used to evaluate prefix, postfix and infix
expressions.
Expression Conversion: It can be used to convert one form of
expression(prefix,postfix or infix) to one another.
Syntax Parsing: Many compilers use a stack for parsing the
syntax of
expressions.
Backtracking: It can be used for back traversal of steps in a
problem solution.
Parenthesis Checking: Stack is used to check the proper opening
and closing of parenthesis.
String Reversal: It can be used to reverse a string.
Function Call: Stack is used to keep information about the active
functions or subroutines.
Data-structures

Using List as Stack in Python:
The concept of Stack implementation is easy in Python ,
because it support inbuilt functions (append() and pop())
for stack implementation.By Using these functions make
the code short and simple for stack implementation.
To add an item to the top of the list, i.e., to push an item,
we use append() function and to pop out an element we
use pop() function. These functions work quiet efficiently
and fast in end operations.
Data-structures

Stack e.g. program:
stack = [5, 9, 3]
stack.append(7)
stack.append(11)
print(stack)
print(stack.pop()
) print(stack)
print(stack.pop()
) print(stack)
OUTPUT
[5, 9, 3, 7, 11]
11
[5, 9, 3, 7]
7
[5, 9, 3]
Data-structures

class Stack:
def init
(self):
self.items = []
def is_empty(self):
return self.items == [] def
push(self, data):
self.items.append(data) def
pop(self):
return self.items.pop()
s = Stack() while
True:
print('Press 1 for push')
print('Press 2 for pop')
print('Press 3 for quit')
do = int(input('What would
you like to do'))
Stack interactive
program:
Data-structures
if do == 1:
n=int(input("enter a number to push")) s.push(n)
elif do == 2:
if s.is_empty(): print('Stack is empty.')
else:
print('Popped value: ', s.pop()) elif
operation ==
3:

Data -structures for class 12 , easy ppt

Recommended

More Related Content

Similar to Data -structures for class 12 , easy ppt (20)

Recently uploaded (20)

Data -structures for class 12 , easy ppt